diff --git a/x-pack/plugins/monitoring/common/index.js b/x-pack/plugins/monitoring/common/index.ts
similarity index 95%
rename from x-pack/plugins/monitoring/common/index.js
rename to x-pack/plugins/monitoring/common/index.ts
index b71419e8c3dd..371a4172ebbc 100644
--- a/x-pack/plugins/monitoring/common/index.js
+++ b/x-pack/plugins/monitoring/common/index.ts
@@ -5,4 +5,5 @@
  * 2.0.
  */
 
+// @ts-ignore
 export { formatTimestampToDuration } from './format_timestamp_to_duration';
diff --git a/x-pack/plugins/monitoring/server/lib/alerts/fetch_status.test.ts b/x-pack/plugins/monitoring/server/lib/alerts/fetch_status.test.ts
index ffcab2756859..36d2ef1bdba0 100644
--- a/x-pack/plugins/monitoring/server/lib/alerts/fetch_status.test.ts
+++ b/x-pack/plugins/monitoring/server/lib/alerts/fetch_status.test.ts
@@ -46,7 +46,6 @@ describe('fetchStatus', () => {
     triggeredMS: 0,
   };
   let alertStates: AlertState[] = [];
-  const licenseService = null;
   const rulesClient = {
     find: jest.fn(() => ({
       total: 1,
@@ -74,7 +73,7 @@ describe('fetchStatus', () => {
   });
 
   it('should fetch from the alerts client', async () => {
-    const status = await fetchStatus(rulesClient as any, licenseService as any, alertTypes, [
+    const status = await fetchStatus(rulesClient as any, alertTypes, [
       defaultClusterState.clusterUuid,
     ]);
     expect(status).toEqual({
@@ -96,7 +95,7 @@ describe('fetchStatus', () => {
       },
     ];
 
-    const status = await fetchStatus(rulesClient as any, licenseService as any, alertTypes, [
+    const status = await fetchStatus(rulesClient as any, alertTypes, [
       defaultClusterState.clusterUuid,
     ]);
     expect(Object.values(status).length).toBe(1);
@@ -105,9 +104,7 @@ describe('fetchStatus', () => {
   });
 
   it('should pass in the right filter to the alerts client', async () => {
-    await fetchStatus(rulesClient as any, licenseService as any, alertTypes, [
-      defaultClusterState.clusterUuid,
-    ]);
+    await fetchStatus(rulesClient as any, alertTypes, [defaultClusterState.clusterUuid]);
     expect((rulesClient.find as jest.Mock).mock.calls[0][0].options.filter).toBe(
       `alert.attributes.alertTypeId:${alertType}`
     );
@@ -118,7 +115,7 @@ describe('fetchStatus', () => {
       alertTypeState: null,
     })) as any;
 
-    const status = await fetchStatus(rulesClient as any, licenseService as any, alertTypes, [
+    const status = await fetchStatus(rulesClient as any, alertTypes, [
       defaultClusterState.clusterUuid,
     ]);
     expect(status[alertType].states.length).toEqual(0);
@@ -130,7 +127,7 @@ describe('fetchStatus', () => {
       data: [],
     })) as any;
 
-    const status = await fetchStatus(rulesClient as any, licenseService as any, alertTypes, [
+    const status = await fetchStatus(rulesClient as any, alertTypes, [
       defaultClusterState.clusterUuid,
     ]);
     expect(status).toEqual({});
@@ -146,7 +143,6 @@ describe('fetchStatus', () => {
     };
     await fetchStatus(
       rulesClient as any,
-      customLicenseService as any,
       [ALERT_CLUSTER_HEALTH],
       [defaultClusterState.clusterUuid]
     );
@@ -183,7 +179,6 @@ describe('fetchStatus', () => {
     };
     const status = await fetchStatus(
       customRulesClient as any,
-      licenseService as any,
       [ALERT_CPU_USAGE, ALERT_DISK_USAGE, ALERT_MISSING_MONITORING_DATA],
       [defaultClusterState.clusterUuid]
     );
diff --git a/x-pack/plugins/monitoring/server/lib/alerts/fetch_status.ts b/x-pack/plugins/monitoring/server/lib/alerts/fetch_status.ts
index f4fd792ddf92..4a20dcb0fdf2 100644
--- a/x-pack/plugins/monitoring/server/lib/alerts/fetch_status.ts
+++ b/x-pack/plugins/monitoring/server/lib/alerts/fetch_status.ts
@@ -14,11 +14,9 @@ import {
   CommonAlertFilter,
 } from '../../../common/types/alerts';
 import { ALERTS } from '../../../common/constants';
-import { MonitoringLicenseService } from '../../types';
 
 export async function fetchStatus(
   rulesClient: RulesClient,
-  licenseService: MonitoringLicenseService,
   alertTypes: string[] | undefined,
   clusterUuids: string[],
   filters: CommonAlertFilter[] = []
diff --git a/x-pack/plugins/monitoring/server/lib/apm/_apm_stats.js b/x-pack/plugins/monitoring/server/lib/apm/_apm_stats.ts
similarity index 73%
rename from x-pack/plugins/monitoring/server/lib/apm/_apm_stats.js
rename to x-pack/plugins/monitoring/server/lib/apm/_apm_stats.ts
index 64450405b326..0068d521055e 100644
--- a/x-pack/plugins/monitoring/server/lib/apm/_apm_stats.js
+++ b/x-pack/plugins/monitoring/server/lib/apm/_apm_stats.ts
@@ -5,14 +5,14 @@
  * 2.0.
  */
 
-import { get } from 'lodash';
+import type { ElasticsearchResponse } from '../../../common/types/es';
 
-const getMemPath = (cgroup) =>
+const getMemPath = (cgroup?: string) =>
   cgroup
     ? 'beats_stats.metrics.beat.cgroup.memory.mem.usage.bytes'
     : 'beats_stats.metrics.beat.memstats.rss';
 
-export const getDiffCalculation = (max, min) => {
+export const getDiffCalculation = (max: number | null, min: number | null) => {
   // no need to test max >= 0, but min <= 0 which is normal for a derivative after restart
   // because we are aggregating/collapsing on ephemeral_ids
   if (max !== null && min !== null && max >= 0 && min >= 0 && max >= min) {
@@ -30,7 +30,7 @@ export const apmAggFilterPath = [
   'aggregations.max_mem_total.value',
   'aggregations.versions.buckets',
 ];
-export const apmUuidsAgg = (maxBucketSize, cgroup) => ({
+export const apmUuidsAgg = (maxBucketSize?: string, cgroup?: string) => ({
   total: {
     cardinality: {
       field: 'beats_stats.beat.uuid',
@@ -92,14 +92,16 @@ export const apmUuidsAgg = (maxBucketSize, cgroup) => ({
   },
 });
 
-export const apmAggResponseHandler = (response) => {
-  const apmTotal = get(response, 'aggregations.total.value', 0);
+export const apmAggResponseHandler = (response: ElasticsearchResponse) => {
+  const apmTotal = response.aggregations?.total.value ?? 0;
 
-  const eventsTotalMax = get(response, 'aggregations.max_events_total.value', 0);
-  const eventsTotalMin = get(response, 'aggregations.min_events_total.value', 0);
-  const memMax = get(response, 'aggregations.max_mem_total.value', 0);
-  const memMin = get(response, 'aggregations.min_mem_total.value', 0);
-  const versions = get(response, 'aggregations.versions.buckets', []).map(({ key }) => key);
+  const eventsTotalMax = response.aggregations?.max_events_total.value ?? 0;
+  const eventsTotalMin = response.aggregations?.min_events_total.value ?? 0;
+  const memMax = response.aggregations?.max_mem_total.value ?? 0;
+  const memMin = response.aggregations?.min_mem_total.value ?? 0;
+  const versions = (response.aggregations?.versions.buckets ?? []).map(
+    ({ key }: { key: string }) => key
+  );
 
   return {
     apmTotal,
diff --git a/x-pack/plugins/monitoring/server/lib/apm/_get_time_of_last_event.ts b/x-pack/plugins/monitoring/server/lib/apm/_get_time_of_last_event.ts
index 398428f89a4b..0ad1ff7370a9 100644
--- a/x-pack/plugins/monitoring/server/lib/apm/_get_time_of_last_event.ts
+++ b/x-pack/plugins/monitoring/server/lib/apm/_get_time_of_last_event.ts
@@ -5,9 +5,7 @@
  * 2.0.
  */
 
-// @ts-ignore
 import { createApmQuery } from './create_apm_query';
-// @ts-ignore
 import { ApmClusterMetric } from '../metrics';
 import { LegacyRequest } from '../../types';
 import { ElasticsearchResponse } from '../../../common/types/es';
diff --git a/x-pack/plugins/monitoring/server/lib/apm/create_apm_query.js b/x-pack/plugins/monitoring/server/lib/apm/create_apm_query.ts
similarity index 63%
rename from x-pack/plugins/monitoring/server/lib/apm/create_apm_query.js
rename to x-pack/plugins/monitoring/server/lib/apm/create_apm_query.ts
index 1680fcdfdb22..63c56607a68e 100644
--- a/x-pack/plugins/monitoring/server/lib/apm/create_apm_query.js
+++ b/x-pack/plugins/monitoring/server/lib/apm/create_apm_query.ts
@@ -5,8 +5,7 @@
  * 2.0.
  */
 
-import { defaults } from 'lodash';
-import { ApmMetric } from '../metrics';
+import { ApmMetric, ApmMetricFields } from '../metrics';
 import { createQuery } from '../create_query';
 
 /**
@@ -14,14 +13,23 @@ import { createQuery } from '../create_query';
  *
  * @param {Object} options The options to pass to {@code createQuery}
  */
-export function createApmQuery(options = {}) {
-  options = defaults(options, {
-    filters: [],
+export function createApmQuery(options: {
+  filters?: any[];
+  types?: string[];
+  metric?: ApmMetricFields;
+  uuid?: string;
+  clusterUuid: string;
+  start?: number;
+  end?: number;
+}) {
+  const opts = {
+    filters: [] as any[],
     metric: ApmMetric.getMetricFields(),
     types: ['stats', 'beats_stats'],
-  });
+    ...(options ?? {}),
+  };
 
-  options.filters.push({
+  opts.filters.push({
     bool: {
       must: {
         term: {
@@ -31,5 +39,5 @@ export function createApmQuery(options = {}) {
     },
   });
 
-  return createQuery(options);
+  return createQuery(opts);
 }
diff --git a/x-pack/plugins/monitoring/server/lib/apm/get_apm_info.ts b/x-pack/plugins/monitoring/server/lib/apm/get_apm_info.ts
index 3721bf873a41..5b2f8424a566 100644
--- a/x-pack/plugins/monitoring/server/lib/apm/get_apm_info.ts
+++ b/x-pack/plugins/monitoring/server/lib/apm/get_apm_info.ts
@@ -66,7 +66,7 @@ export function handleResponse(
     eventsTotal: getDiffCalculation(eventsTotalLast, eventsTotalFirst),
     eventsEmitted: getDiffCalculation(eventsEmittedLast, eventsEmittedFirst),
     eventsDropped: getDiffCalculation(eventsDroppedLast, eventsDroppedFirst),
-    bytesWritten: getDiffCalculation(bytesWrittenLast, bytesWrittenFirst),
+    bytesWritten: getDiffCalculation(Number(bytesWrittenLast), Number(bytesWrittenFirst)),
     config: {
       container: config.get('monitoring.ui.container.apm.enabled'),
     },
diff --git a/x-pack/plugins/monitoring/server/lib/apm/get_apms.ts b/x-pack/plugins/monitoring/server/lib/apm/get_apms.ts
index be3bb6fdfd66..7089a0507107 100644
--- a/x-pack/plugins/monitoring/server/lib/apm/get_apms.ts
+++ b/x-pack/plugins/monitoring/server/lib/apm/get_apms.ts
@@ -49,9 +49,11 @@ export function handleResponse(response: ElasticsearchResponse, start: number, e
 
     //  add the beat
     const rateOptions = {
-      hitTimestamp: stats?.timestamp ?? hit._source['@timestamp'],
+      hitTimestamp: stats?.timestamp ?? hit._source['@timestamp'] ?? null,
       earliestHitTimestamp:
-        earliestStats?.timestamp ?? hit.inner_hits?.earliest.hits?.hits[0]._source['@timestamp'],
+        earliestStats?.timestamp ??
+        hit.inner_hits?.earliest.hits?.hits[0]._source['@timestamp'] ??
+        null,
       timeWindowMin: start,
       timeWindowMax: end,
     };
diff --git a/x-pack/plugins/monitoring/server/lib/apm/get_apms_for_clusters.js b/x-pack/plugins/monitoring/server/lib/apm/get_apms_for_clusters.ts
similarity index 85%
rename from x-pack/plugins/monitoring/server/lib/apm/get_apms_for_clusters.js
rename to x-pack/plugins/monitoring/server/lib/apm/get_apms_for_clusters.ts
index 0c96e0e23058..e99ce0da1ef1 100644
--- a/x-pack/plugins/monitoring/server/lib/apm/get_apms_for_clusters.js
+++ b/x-pack/plugins/monitoring/server/lib/apm/get_apms_for_clusters.ts
@@ -5,14 +5,15 @@
  * 2.0.
  */
 
-import { get } from 'lodash';
+import { LegacyRequest, Cluster } from '../../types';
 import { checkParam } from '../error_missing_required';
 import { createApmQuery } from './create_apm_query';
 import { ApmMetric } from '../metrics';
 import { apmAggResponseHandler, apmUuidsAgg, apmAggFilterPath } from './_apm_stats';
 import { getTimeOfLastEvent } from './_get_time_of_last_event';
+import { ElasticsearchResponse } from '../../../common/types/es';
 
-export function handleResponse(clusterUuid, response) {
+export function handleResponse(clusterUuid: string, response: ElasticsearchResponse) {
   const { apmTotal, totalEvents, memRss, versions } = apmAggResponseHandler(response);
 
   // combine stats
@@ -31,7 +32,11 @@ export function handleResponse(clusterUuid, response) {
   };
 }
 
-export function getApmsForClusters(req, apmIndexPattern, clusters) {
+export function getApmsForClusters(
+  req: LegacyRequest,
+  apmIndexPattern: string,
+  clusters: Cluster[]
+) {
   checkParam(apmIndexPattern, 'apmIndexPattern in apms/getApmsForClusters');
 
   const start = req.payload.timeRange.min;
@@ -42,7 +47,7 @@ export function getApmsForClusters(req, apmIndexPattern, clusters) {
 
   return Promise.all(
     clusters.map(async (cluster) => {
-      const clusterUuid = get(cluster, 'elasticsearch.cluster.id', cluster.cluster_uuid);
+      const clusterUuid = cluster.elasticsearch?.cluster?.id ?? cluster.cluster_uuid;
       const params = {
         index: apmIndexPattern,
         size: 0,
diff --git a/x-pack/plugins/monitoring/server/lib/apm/get_stats.js b/x-pack/plugins/monitoring/server/lib/apm/get_stats.ts
similarity index 80%
rename from x-pack/plugins/monitoring/server/lib/apm/get_stats.js
rename to x-pack/plugins/monitoring/server/lib/apm/get_stats.ts
index 2abd81e325f5..ea71229bac81 100644
--- a/x-pack/plugins/monitoring/server/lib/apm/get_stats.js
+++ b/x-pack/plugins/monitoring/server/lib/apm/get_stats.ts
@@ -6,16 +6,17 @@
  */
 
 import moment from 'moment';
+import { LegacyRequest } from '../../types';
 import { checkParam } from '../error_missing_required';
 import { createApmQuery } from './create_apm_query';
 import { apmAggFilterPath, apmUuidsAgg, apmAggResponseHandler } from './_apm_stats';
 import { getTimeOfLastEvent } from './_get_time_of_last_event';
+import type { ElasticsearchResponse } from '../../../common/types/es';
 
-export function handleResponse(...args) {
-  const { apmTotal, totalEvents, bytesSent } = apmAggResponseHandler(...args);
+export function handleResponse(response: ElasticsearchResponse) {
+  const { apmTotal, totalEvents } = apmAggResponseHandler(response);
 
   return {
-    bytesSent,
     totalEvents,
     apms: {
       total: apmTotal,
@@ -23,7 +24,7 @@ export function handleResponse(...args) {
   };
 }
 
-export async function getStats(req, apmIndexPattern, clusterUuid) {
+export async function getStats(req: LegacyRequest, apmIndexPattern: string, clusterUuid: string) {
   checkParam(apmIndexPattern, 'apmIndexPattern in getBeats');
 
   const config = req.server.config();
@@ -60,7 +61,7 @@ export async function getStats(req, apmIndexPattern, clusterUuid) {
     }),
   ]);
 
-  const formattedResponse = handleResponse(response, start, end);
+  const formattedResponse = handleResponse(response);
   return {
     ...formattedResponse,
     timeOfLastEvent,
diff --git a/x-pack/plugins/monitoring/server/lib/apm/index.js b/x-pack/plugins/monitoring/server/lib/apm/index.ts
similarity index 100%
rename from x-pack/plugins/monitoring/server/lib/apm/index.js
rename to x-pack/plugins/monitoring/server/lib/apm/index.ts
diff --git a/x-pack/plugins/monitoring/server/lib/beats/__fixtures__/get_listing_response.js b/x-pack/plugins/monitoring/server/lib/beats/__fixtures__/get_listing_response.ts
similarity index 100%
rename from x-pack/plugins/monitoring/server/lib/beats/__fixtures__/get_listing_response.js
rename to x-pack/plugins/monitoring/server/lib/beats/__fixtures__/get_listing_response.ts
diff --git a/x-pack/plugins/monitoring/server/lib/beats/_beats_stats.js b/x-pack/plugins/monitoring/server/lib/beats/_beats_stats.ts
similarity index 74%
rename from x-pack/plugins/monitoring/server/lib/beats/_beats_stats.js
rename to x-pack/plugins/monitoring/server/lib/beats/_beats_stats.ts
index 0d4dc0ba59d1..c2ddadcf7ebf 100644
--- a/x-pack/plugins/monitoring/server/lib/beats/_beats_stats.js
+++ b/x-pack/plugins/monitoring/server/lib/beats/_beats_stats.ts
@@ -5,9 +5,10 @@
  * 2.0.
  */
 
-import { upperFirst, get } from 'lodash';
+import { upperFirst } from 'lodash';
+import type { BeatsElasticsearchResponse, BucketCount } from './types';
 
-export const getDiffCalculation = (max, min) => {
+export const getDiffCalculation = (max: number | null, min: number | null) => {
   // no need to test max >= 0, but min <= 0 which is normal for a derivative after restart
   // because we are aggregating/collapsing on ephemeral_ids
   if (max !== null && min !== null && max >= 0 && min >= 0 && max >= min) {
@@ -27,7 +28,7 @@ export const beatsAggFilterPath = [
   'aggregations.max_bytes_sent_total.value',
 ];
 
-export const beatsUuidsAgg = (maxBucketSize) => ({
+export const beatsUuidsAgg = (maxBucketSize: string) => ({
   types: {
     terms: {
       field: 'beats_stats.beat.type',
@@ -98,24 +99,24 @@ export const beatsUuidsAgg = (maxBucketSize) => ({
   },
 });
 
-export const beatsAggResponseHandler = (response) => {
+export const beatsAggResponseHandler = (response?: BeatsElasticsearchResponse) => {
   // beat types stat
-  const buckets = get(response, 'aggregations.types.buckets', []);
-  const beatTotal = get(response, 'aggregations.total.value', 0);
-  const beatTypes = buckets.reduce((types, typeBucket) => {
+  const buckets = response?.aggregations?.types?.buckets ?? [];
+  const beatTotal = response?.aggregations?.total.value ?? 0;
+  const beatTypes = buckets.reduce((types: BucketCount<{ type: string }>, typeBucket) => {
     return [
       ...types,
       {
         type: upperFirst(typeBucket.key),
-        count: get(typeBucket, 'uuids.buckets.length'),
+        count: typeBucket.uuids.buckets.length,
       },
     ];
   }, []);
 
-  const eventsTotalMax = get(response, 'aggregations.max_events_total.value', 0);
-  const eventsTotalMin = get(response, 'aggregations.min_events_total.value', 0);
-  const bytesSentMax = get(response, 'aggregations.max_bytes_sent_total.value', 0);
-  const bytesSentMin = get(response, 'aggregations.min_bytes_sent_total.value', 0);
+  const eventsTotalMax = response?.aggregations?.max_events_total.value ?? 0;
+  const eventsTotalMin = response?.aggregations?.min_events_total.value ?? 0;
+  const bytesSentMax = response?.aggregations?.max_bytes_sent_total.value ?? 0;
+  const bytesSentMin = response?.aggregations?.min_bytes_sent_total.value ?? 0;
 
   return {
     beatTotal,
diff --git a/x-pack/plugins/monitoring/server/lib/beats/create_beats_query.js b/x-pack/plugins/monitoring/server/lib/beats/create_beats_query.ts
similarity index 71%
rename from x-pack/plugins/monitoring/server/lib/beats/create_beats_query.js
rename to x-pack/plugins/monitoring/server/lib/beats/create_beats_query.ts
index c6ec39ed3ba2..b013cd8234c4 100644
--- a/x-pack/plugins/monitoring/server/lib/beats/create_beats_query.js
+++ b/x-pack/plugins/monitoring/server/lib/beats/create_beats_query.ts
@@ -5,8 +5,7 @@
  * 2.0.
  */
 
-import { defaults } from 'lodash';
-import { BeatsMetric } from '../metrics';
+import { BeatsMetric, BeatsMetricFields } from '../metrics';
 import { createQuery } from '../create_query';
 
 /**
@@ -17,15 +16,24 @@ import { createQuery } from '../create_query';
  *
  * @param {Object} options The options to pass to {@code createQuery}
  */
-export function createBeatsQuery(options = {}) {
-  options = defaults(options, {
-    filters: [],
+export function createBeatsQuery(options: {
+  filters?: any[];
+  types?: string[];
+  metric?: BeatsMetricFields;
+  uuid?: string;
+  clusterUuid: string;
+  start?: number;
+  end?: number;
+}) {
+  const opts = {
+    filters: [] as any[],
     metric: BeatsMetric.getMetricFields(),
     types: ['stats', 'beats_stats'],
-  });
+    ...(options ?? {}),
+  };
 
   // avoid showing APM Server stats alongside other Beats because APM Server will have its own UI
-  options.filters.push({
+  opts.filters.push({
     bool: {
       must_not: {
         term: {
@@ -35,5 +43,5 @@ export function createBeatsQuery(options = {}) {
     },
   });
 
-  return createQuery(options);
+  return createQuery(opts);
 }
diff --git a/x-pack/plugins/monitoring/server/lib/beats/get_beat_summary.ts b/x-pack/plugins/monitoring/server/lib/beats/get_beat_summary.ts
index d67f32e64ba7..07169b54cb61 100644
--- a/x-pack/plugins/monitoring/server/lib/beats/get_beat_summary.ts
+++ b/x-pack/plugins/monitoring/server/lib/beats/get_beat_summary.ts
@@ -11,7 +11,7 @@ import { ElasticsearchResponse } from '../../../common/types/es';
 // @ts-ignore
 import { checkParam } from '../error_missing_required';
 // @ts-ignore
-import { createBeatsQuery } from './create_beats_query.js';
+import { createBeatsQuery } from './create_beats_query';
 // @ts-ignore
 import { getDiffCalculation } from './_beats_stats';
 
@@ -67,7 +67,7 @@ export function handleResponse(response: ElasticsearchResponse, beatUuid: string
     eventsTotal: getDiffCalculation(eventsTotalLast, eventsTotalFirst) ?? null,
     eventsEmitted: getDiffCalculation(eventsEmittedLast, eventsEmittedFirst) ?? null,
     eventsDropped: getDiffCalculation(eventsDroppedLast, eventsDroppedFirst) ?? null,
-    bytesWritten: getDiffCalculation(bytesWrittenLast, bytesWrittenFirst) ?? null,
+    bytesWritten: getDiffCalculation(Number(bytesWrittenLast), Number(bytesWrittenFirst)) ?? null,
     handlesHardLimit,
     handlesSoftLimit,
   };
diff --git a/x-pack/plugins/monitoring/server/lib/beats/get_beats.ts b/x-pack/plugins/monitoring/server/lib/beats/get_beats.ts
index fff2b55cf261..85a4bb61f557 100644
--- a/x-pack/plugins/monitoring/server/lib/beats/get_beats.ts
+++ b/x-pack/plugins/monitoring/server/lib/beats/get_beats.ts
@@ -19,14 +19,14 @@ import { LegacyRequest } from '../../types';
 import { ElasticsearchResponse } from '../../../common/types/es';
 
 interface Beat {
-  uuid: string | undefined;
-  name: string | undefined;
-  type: string | undefined;
-  output: string | undefined;
+  uuid?: string;
+  name?: string;
+  type?: string;
+  output?: string;
   total_events_rate: number;
   bytes_sent_rate: number;
-  memory: number | undefined;
-  version: string | undefined;
+  memory?: number;
+  version?: string;
   errors: any;
 }
 
@@ -63,9 +63,9 @@ export function handleResponse(response: ElasticsearchResponse, start: number, e
 
     //  add the beat
     const rateOptions = {
-      hitTimestamp: stats?.timestamp ?? hit._source['@timestamp'],
+      hitTimestamp: stats?.timestamp ?? hit._source['@timestamp']!,
       earliestHitTimestamp:
-        earliestStats?.timestamp ?? hit.inner_hits?.earliest.hits?.hits[0]._source['@timestamp'],
+        earliestStats?.timestamp ?? hit.inner_hits?.earliest.hits?.hits[0]._source['@timestamp']!,
       timeWindowMin: start,
       timeWindowMax: end,
     };
@@ -96,8 +96,8 @@ export function handleResponse(response: ElasticsearchResponse, start: number, e
       name: stats?.beat?.name,
       type: upperFirst(stats?.beat?.type),
       output: upperFirst(statsMetrics?.libbeat?.output?.type),
-      total_events_rate: totalEventsRate,
-      bytes_sent_rate: bytesSentRate,
+      total_events_rate: totalEventsRate!,
+      bytes_sent_rate: bytesSentRate!,
       errors,
       memory:
         hit._source.beats_stats?.metrics?.beat?.memstats?.memory_alloc ??
diff --git a/x-pack/plugins/monitoring/server/lib/beats/get_beats_for_clusters.js b/x-pack/plugins/monitoring/server/lib/beats/get_beats_for_clusters.ts
similarity index 79%
rename from x-pack/plugins/monitoring/server/lib/beats/get_beats_for_clusters.js
rename to x-pack/plugins/monitoring/server/lib/beats/get_beats_for_clusters.ts
index e7c4771dd601..3a0720f7ca19 100644
--- a/x-pack/plugins/monitoring/server/lib/beats/get_beats_for_clusters.js
+++ b/x-pack/plugins/monitoring/server/lib/beats/get_beats_for_clusters.ts
@@ -5,13 +5,14 @@
  * 2.0.
  */
 
-import { get } from 'lodash';
 import { checkParam } from '../error_missing_required';
 import { BeatsClusterMetric } from '../metrics';
 import { createBeatsQuery } from './create_beats_query';
 import { beatsAggFilterPath, beatsUuidsAgg, beatsAggResponseHandler } from './_beats_stats';
+import type { ElasticsearchResponse } from '../../../common/types/es';
+import { LegacyRequest, Cluster } from '../../types';
 
-export function handleResponse(clusterUuid, response) {
+export function handleResponse(clusterUuid: string, response: ElasticsearchResponse) {
   const { beatTotal, beatTypes, totalEvents, bytesSent } = beatsAggResponseHandler(response);
 
   // combine stats
@@ -30,7 +31,11 @@ export function handleResponse(clusterUuid, response) {
   };
 }
 
-export function getBeatsForClusters(req, beatsIndexPattern, clusters) {
+export function getBeatsForClusters(
+  req: LegacyRequest,
+  beatsIndexPattern: string,
+  clusters: Cluster[]
+) {
   checkParam(beatsIndexPattern, 'beatsIndexPattern in beats/getBeatsForClusters');
 
   const start = req.payload.timeRange.min;
@@ -40,7 +45,7 @@ export function getBeatsForClusters(req, beatsIndexPattern, clusters) {
 
   return Promise.all(
     clusters.map(async (cluster) => {
-      const clusterUuid = get(cluster, 'elasticsearch.cluster.id', cluster.cluster_uuid);
+      const clusterUuid = cluster.elasticsearch?.cluster?.id ?? cluster.cluster_uuid;
       const params = {
         index: beatsIndexPattern,
         size: 0,
@@ -53,7 +58,7 @@ export function getBeatsForClusters(req, beatsIndexPattern, clusters) {
             clusterUuid,
             metric: BeatsClusterMetric.getMetricFields(), // override default of BeatMetric.getMetricFields
           }),
-          aggs: beatsUuidsAgg(maxBucketSize),
+          aggs: beatsUuidsAgg(maxBucketSize!),
         },
       };
 
diff --git a/x-pack/plugins/monitoring/server/lib/beats/get_latest_stats.js b/x-pack/plugins/monitoring/server/lib/beats/get_latest_stats.ts
similarity index 72%
rename from x-pack/plugins/monitoring/server/lib/beats/get_latest_stats.js
rename to x-pack/plugins/monitoring/server/lib/beats/get_latest_stats.ts
index fb40df115d19..684b0d6301e1 100644
--- a/x-pack/plugins/monitoring/server/lib/beats/get_latest_stats.js
+++ b/x-pack/plugins/monitoring/server/lib/beats/get_latest_stats.ts
@@ -5,17 +5,19 @@
  * 2.0.
  */
 
-import { upperFirst, get } from 'lodash';
+import { upperFirst } from 'lodash';
+import { LegacyRequest } from '../../types';
 import { checkParam } from '../error_missing_required';
 import { createBeatsQuery } from './create_beats_query';
+import type { BeatsElasticsearchResponse, BucketCount } from './types';
 
-export function handleResponse(response) {
-  const aggs = get(response, 'aggregations');
+export function handleResponse(response?: BeatsElasticsearchResponse) {
+  const aggs = response?.aggregations;
 
-  const getTimeRangeCount = (name) => {
-    const lastActiveBuckets = get(aggs, 'active_counts.buckets', []);
+  const getTimeRangeCount = (name: string) => {
+    const lastActiveBuckets = aggs?.active_counts?.buckets ?? [];
     const rangeBucket = lastActiveBuckets.find((bucket) => bucket.key === name);
-    return get(rangeBucket, 'uuids.buckets.length');
+    return rangeBucket?.uuids.buckets.length;
   };
 
   // aggregations are not ordered, so we find the bucket for each timestamp range
@@ -34,25 +36,31 @@ export function handleResponse(response) {
     { range: 'last1d', count: last1dCount },
   ];
 
-  const latestVersions = get(aggs, 'versions.buckets', []).reduce((accum, current) => {
-    return [
-      ...accum,
-      {
-        version: current.key,
-        count: get(current, 'uuids.buckets.length'),
-      },
-    ];
-  }, []);
+  const latestVersions = (aggs?.versions?.buckets ?? []).reduce(
+    (accum: BucketCount<{ version: string }>, current) => {
+      return [
+        ...accum,
+        {
+          version: current.key,
+          count: current.uuids.buckets.length,
+        },
+      ];
+    },
+    []
+  );
 
-  const latestTypes = get(aggs, 'types.buckets', []).reduce((accum, current) => {
-    return [
-      ...accum,
-      {
-        type: upperFirst(current.key),
-        count: get(current, 'uuids.buckets.length'),
-      },
-    ];
-  }, []);
+  const latestTypes = (aggs?.types?.buckets ?? []).reduce(
+    (accum: BucketCount<{ type: string }>, current) => {
+      return [
+        ...accum,
+        {
+          type: upperFirst(current.key),
+          count: current.uuids.buckets.length,
+        },
+      ];
+    },
+    []
+  );
 
   return {
     latestActive,
@@ -61,7 +69,7 @@ export function handleResponse(response) {
   };
 }
 
-export function getLatestStats(req, beatsIndexPattern, clusterUuid) {
+export function getLatestStats(req: LegacyRequest, beatsIndexPattern: string, clusterUuid: string) {
   checkParam(beatsIndexPattern, 'beatsIndexPattern in getBeats');
 
   const config = req.server.config();
diff --git a/x-pack/plugins/monitoring/server/lib/beats/get_stats.js b/x-pack/plugins/monitoring/server/lib/beats/get_stats.ts
similarity index 73%
rename from x-pack/plugins/monitoring/server/lib/beats/get_stats.js
rename to x-pack/plugins/monitoring/server/lib/beats/get_stats.ts
index 3af51d909697..be3f3d88e070 100644
--- a/x-pack/plugins/monitoring/server/lib/beats/get_stats.js
+++ b/x-pack/plugins/monitoring/server/lib/beats/get_stats.ts
@@ -6,12 +6,14 @@
  */
 
 import moment from 'moment';
+import type { BeatsElasticsearchResponse } from './types';
+import { LegacyRequest } from '../../types';
 import { checkParam } from '../error_missing_required';
 import { createBeatsQuery } from './create_beats_query';
 import { beatsAggFilterPath, beatsUuidsAgg, beatsAggResponseHandler } from './_beats_stats';
 
-export function handleResponse(...args) {
-  const { beatTotal, beatTypes, totalEvents, bytesSent } = beatsAggResponseHandler(...args);
+export function handleResponse(response: BeatsElasticsearchResponse) {
+  const { beatTotal, beatTypes, totalEvents, bytesSent } = beatsAggResponseHandler(response);
 
   return {
     total: beatTotal,
@@ -23,7 +25,7 @@ export function handleResponse(...args) {
   };
 }
 
-export async function getStats(req, beatsIndexPattern, clusterUuid) {
+export async function getStats(req: LegacyRequest, beatsIndexPattern: string, clusterUuid: string) {
   checkParam(beatsIndexPattern, 'beatsIndexPattern in getBeats');
 
   const config = req.server.config();
@@ -42,12 +44,12 @@ export async function getStats(req, beatsIndexPattern, clusterUuid) {
         end,
         clusterUuid,
       }),
-      aggs: beatsUuidsAgg(maxBucketSize),
+      aggs: beatsUuidsAgg(maxBucketSize!),
     },
   };
 
   const { callWithRequest } = req.server.plugins.elasticsearch.getCluster('monitoring');
-  const response = await callWithRequest(req, 'search', params);
+  const response: BeatsElasticsearchResponse = await callWithRequest(req, 'search', params);
 
-  return handleResponse(response, start, end);
+  return handleResponse(response);
 }
diff --git a/x-pack/plugins/monitoring/server/lib/beats/index.js b/x-pack/plugins/monitoring/server/lib/beats/index.ts
similarity index 100%
rename from x-pack/plugins/monitoring/server/lib/beats/index.js
rename to x-pack/plugins/monitoring/server/lib/beats/index.ts
diff --git a/x-pack/plugins/monitoring/server/lib/beats/types.ts b/x-pack/plugins/monitoring/server/lib/beats/types.ts
new file mode 100644
index 000000000000..516a4ba58752
--- /dev/null
+++ b/x-pack/plugins/monitoring/server/lib/beats/types.ts
@@ -0,0 +1,38 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0; you may not use this file except in compliance with the Elastic License
+ * 2.0.
+ */
+
+import type { ElasticsearchResponse } from '../../../common/types/es';
+import type { Aggregation } from '../../types';
+
+export type BucketCount<T> = Array<
+  T & {
+    count: number;
+  }
+>;
+
+export interface BeatsElasticsearchResponse extends ElasticsearchResponse {
+  aggregations?: {
+    types?: Aggregation;
+    active_counts?: Aggregation;
+    versions?: Aggregation;
+    total: {
+      value: number;
+    };
+    max_events_total: {
+      value: number;
+    };
+    min_events_total: {
+      value: number;
+    };
+    max_bytes_sent_total: {
+      value: number;
+    };
+    min_bytes_sent_total: {
+      value: number;
+    };
+  };
+}
diff --git a/x-pack/plugins/monitoring/server/lib/calculate_auto.test.js b/x-pack/plugins/monitoring/server/lib/calculate_auto.test.js
index 93a1d1a40ced..934781f7786a 100644
--- a/x-pack/plugins/monitoring/server/lib/calculate_auto.test.js
+++ b/x-pack/plugins/monitoring/server/lib/calculate_auto.test.js
@@ -5,7 +5,7 @@
  * 2.0.
  */
 
-import { calculateAuto } from './calculate_auto.js';
+import { calculateAuto } from './calculate_auto';
 import _ from 'lodash';
 import moment from 'moment';
 
diff --git a/x-pack/plugins/monitoring/server/lib/calculate_auto.js b/x-pack/plugins/monitoring/server/lib/calculate_auto.ts
similarity index 75%
rename from x-pack/plugins/monitoring/server/lib/calculate_auto.js
rename to x-pack/plugins/monitoring/server/lib/calculate_auto.ts
index a6ffda39c79f..817f49d1a586 100644
--- a/x-pack/plugins/monitoring/server/lib/calculate_auto.js
+++ b/x-pack/plugins/monitoring/server/lib/calculate_auto.ts
@@ -5,7 +5,9 @@
  * 2.0.
  */
 
-import moment from 'moment';
+import moment, { Duration } from 'moment';
+
+type RoundingRule = [number | Duration, Duration];
 
 const d = moment.duration;
 const roundingRules = [
@@ -25,18 +27,22 @@ const roundingRules = [
   [d(3, 'week'), d(1, 'week')],
   [d(1, 'year'), d(1, 'month')],
   [Infinity, d(1, 'year')],
-];
+] as RoundingRule[];
 
-function find(rules, check) {
-  function pick(buckets, duration) {
-    const target = duration / buckets;
+function find(
+  rules: RoundingRule[],
+  check: (b: number | Duration, i: Duration, t: number) => Duration | void
+) {
+  function pick(buckets?: number, duration?: Duration): Duration {
+    if (!buckets || !duration) return moment.duration(0);
+    const target = duration.asMilliseconds() / buckets;
     let lastResp;
 
     for (let i = 0; i < rules.length; i++) {
       const rule = rules[i];
       const resp = check(rule[0], rule[1], target);
 
-      if (resp == null) {
+      if (resp === null || resp === undefined) {
         if (lastResp) {
           return lastResp;
         }
@@ -51,11 +57,9 @@ function find(rules, check) {
     return moment.duration(ms, 'ms');
   }
 
-  return function (buckets, duration) {
+  return function (buckets: number, duration: Duration) {
     const interval = pick(buckets, duration);
-    if (interval) {
-      return moment.duration(interval._data);
-    }
+    return interval;
   };
 }
 
diff --git a/x-pack/plugins/monitoring/server/lib/calculate_availability.js b/x-pack/plugins/monitoring/server/lib/calculate_availability.ts
similarity index 90%
rename from x-pack/plugins/monitoring/server/lib/calculate_availability.js
rename to x-pack/plugins/monitoring/server/lib/calculate_availability.ts
index 81b827399079..96a89ee62664 100644
--- a/x-pack/plugins/monitoring/server/lib/calculate_availability.js
+++ b/x-pack/plugins/monitoring/server/lib/calculate_availability.ts
@@ -10,7 +10,7 @@ import moment from 'moment';
  * Return `true` if timestamp of last update is younger than 10 minutes ago
  * If older than, it indicates cluster/instance is offline
  */
-export function calculateAvailability(timestamp) {
+export function calculateAvailability(timestamp: string) {
   const lastUpdate = moment(timestamp); // converts to local time
   return lastUpdate.isAfter(moment().subtract(10, 'minutes')); // compares with local time
 }
diff --git a/x-pack/plugins/monitoring/server/lib/calculate_overall_status.js b/x-pack/plugins/monitoring/server/lib/calculate_overall_status.ts
similarity index 89%
rename from x-pack/plugins/monitoring/server/lib/calculate_overall_status.js
rename to x-pack/plugins/monitoring/server/lib/calculate_overall_status.ts
index 7a0edbdb49e6..78cbb9935045 100644
--- a/x-pack/plugins/monitoring/server/lib/calculate_overall_status.js
+++ b/x-pack/plugins/monitoring/server/lib/calculate_overall_status.ts
@@ -9,7 +9,7 @@
  * A reduce that takes statuses from different products in a cluster and boil
  * it down into a single status
  */
-export function calculateOverallStatus(set) {
+export function calculateOverallStatus(set: Array<string | null | undefined>) {
   return set.reduce((result, current) => {
     if (!current) {
       return result;
diff --git a/x-pack/plugins/monitoring/server/lib/calculate_rate.js b/x-pack/plugins/monitoring/server/lib/calculate_rate.ts
similarity index 81%
rename from x-pack/plugins/monitoring/server/lib/calculate_rate.js
rename to x-pack/plugins/monitoring/server/lib/calculate_rate.ts
index 04d43ca935b9..3e9bdbb5e20f 100644
--- a/x-pack/plugins/monitoring/server/lib/calculate_rate.js
+++ b/x-pack/plugins/monitoring/server/lib/calculate_rate.ts
@@ -20,6 +20,16 @@ import moment from 'moment';
  * 4. From that subtract the earliest timestamp from the time picker
  * This gives you the denominator in millis. Divide it by 1000 to convert to seconds
  */
+
+interface CalculateRateProps {
+  hitTimestamp: string | null;
+  earliestHitTimestamp: string | null;
+  latestTotal?: string | number | null;
+  earliestTotal?: string | number | null;
+  timeWindowMin: number;
+  timeWindowMax: number;
+}
+
 export function calculateRate({
   hitTimestamp = null,
   earliestHitTimestamp = null,
@@ -27,7 +37,7 @@ export function calculateRate({
   earliestTotal = null,
   timeWindowMin,
   timeWindowMax,
-} = {}) {
+}: CalculateRateProps) {
   const nullResult = {
     rate: null,
     isEstimate: false,
@@ -58,9 +68,9 @@ export function calculateRate({
   let rate = null;
   let isEstimate = false;
   if (millisDelta !== 0) {
-    const totalDelta = latestTotal - earliestTotal;
+    const totalDelta = Number(latestTotal) - Number(earliestTotal);
     if (totalDelta < 0) {
-      rate = latestTotal / (millisDelta / 1000); // a restart caused an unwanted negative rate
+      rate = Number(latestTotal) / (millisDelta / 1000); // a restart caused an unwanted negative rate
       isEstimate = true;
     } else {
       rate = totalDelta / (millisDelta / 1000);
diff --git a/x-pack/plugins/monitoring/server/lib/calculate_timeseries_interval.js b/x-pack/plugins/monitoring/server/lib/calculate_timeseries_interval.ts
similarity index 67%
rename from x-pack/plugins/monitoring/server/lib/calculate_timeseries_interval.js
rename to x-pack/plugins/monitoring/server/lib/calculate_timeseries_interval.ts
index c304e75accd3..b4ac19328384 100644
--- a/x-pack/plugins/monitoring/server/lib/calculate_timeseries_interval.js
+++ b/x-pack/plugins/monitoring/server/lib/calculate_timeseries_interval.ts
@@ -9,11 +9,14 @@ import moment from 'moment';
 import { calculateAuto } from './calculate_auto';
 
 export function calculateTimeseriesInterval(
-  lowerBoundInMsSinceEpoch,
-  upperBoundInMsSinceEpoch,
-  minIntervalSeconds
+  lowerBoundInMsSinceEpoch: number,
+  upperBoundInMsSinceEpoch: number,
+  minIntervalSeconds: number
 ) {
   const duration = moment.duration(upperBoundInMsSinceEpoch - lowerBoundInMsSinceEpoch, 'ms');
 
-  return Math.max(minIntervalSeconds, calculateAuto(100, duration).asSeconds());
+  return Math.max(
+    !isNaN(minIntervalSeconds) ? minIntervalSeconds : 0,
+    calculateAuto(100, duration).asSeconds()
+  );
 }
diff --git a/x-pack/plugins/monitoring/server/lib/ccs_utils.js b/x-pack/plugins/monitoring/server/lib/ccs_utils.ts
similarity index 88%
rename from x-pack/plugins/monitoring/server/lib/ccs_utils.js
rename to x-pack/plugins/monitoring/server/lib/ccs_utils.ts
index 08ed8d5a7b35..1d899456913b 100644
--- a/x-pack/plugins/monitoring/server/lib/ccs_utils.js
+++ b/x-pack/plugins/monitoring/server/lib/ccs_utils.ts
@@ -6,8 +6,18 @@
  */
 
 import { isFunction, get } from 'lodash';
+import type { MonitoringConfig } from '../config';
 
-export function appendMetricbeatIndex(config, indexPattern, ccs, bypass = false) {
+type Config = Partial<MonitoringConfig> & {
+  get?: (key: string) => any;
+};
+
+export function appendMetricbeatIndex(
+  config: Config,
+  indexPattern: string,
+  ccs?: string,
+  bypass: boolean = false
+) {
   if (bypass) {
     return indexPattern;
   }
@@ -39,7 +49,12 @@ export function appendMetricbeatIndex(config, indexPattern, ccs, bypass = false)
  * @param  {String} ccs The optional cluster-prefix to prepend.
  * @return {String} The index pattern with the {@code cluster} prefix appropriately prepended.
  */
-export function prefixIndexPattern(config, indexPattern, ccs, monitoringIndicesOnly = false) {
+export function prefixIndexPattern(
+  config: Config,
+  indexPattern: string,
+  ccs?: string,
+  monitoringIndicesOnly: boolean = false
+) {
   let ccsEnabled = false;
   // TODO: NP
   // This function is called with both NP config and LP config
@@ -102,7 +117,7 @@ export function prefixIndexPattern(config, indexPattern, ccs, monitoringIndicesO
  * @param  {String} indexName The index's name, possibly including the cross-cluster prefix
  * @return {String} {@code null} if none. Otherwise the cluster prefix.
  */
-export function parseCrossClusterPrefix(indexName) {
+export function parseCrossClusterPrefix(indexName: string) {
   const colonIndex = indexName.indexOf(':');
 
   if (colonIndex === -1) {
diff --git a/x-pack/plugins/monitoring/server/lib/cluster/get_cluster_stats.js b/x-pack/plugins/monitoring/server/lib/cluster/get_cluster_stats.ts
similarity index 91%
rename from x-pack/plugins/monitoring/server/lib/cluster/get_cluster_stats.js
rename to x-pack/plugins/monitoring/server/lib/cluster/get_cluster_stats.ts
index 4dece136158a..c671765a4454 100644
--- a/x-pack/plugins/monitoring/server/lib/cluster/get_cluster_stats.js
+++ b/x-pack/plugins/monitoring/server/lib/cluster/get_cluster_stats.ts
@@ -6,8 +6,9 @@
  */
 
 import { badRequest, notFound } from '@hapi/boom';
-import { getClustersStats } from './get_clusters_stats';
 import { i18n } from '@kbn/i18n';
+import { LegacyRequest } from '../../types';
+import { getClustersStats } from './get_clusters_stats';
 
 /**
  * This will fetch the cluster stats and cluster state as a single object for the cluster specified by the {@code req}.
@@ -17,7 +18,7 @@ import { i18n } from '@kbn/i18n';
  * @param {String} clusterUuid The requested cluster's UUID
  * @return {Promise} The object cluster response.
  */
-export function getClusterStats(req, esIndexPattern, clusterUuid) {
+export function getClusterStats(req: LegacyRequest, esIndexPattern: string, clusterUuid: string) {
   if (!clusterUuid) {
     throw badRequest(
       i18n.translate('xpack.monitoring.clusterStats.uuidNotSpecifiedErrorMessage', {
diff --git a/x-pack/plugins/monitoring/server/lib/cluster/get_clusters_from_request.js b/x-pack/plugins/monitoring/server/lib/cluster/get_clusters_from_request.ts
similarity index 90%
rename from x-pack/plugins/monitoring/server/lib/cluster/get_clusters_from_request.js
rename to x-pack/plugins/monitoring/server/lib/cluster/get_clusters_from_request.ts
index 9ef309cee731..ab421312244f 100644
--- a/x-pack/plugins/monitoring/server/lib/cluster/get_clusters_from_request.js
+++ b/x-pack/plugins/monitoring/server/lib/cluster/get_clusters_from_request.ts
@@ -6,8 +6,9 @@
  */
 
 import { notFound } from '@hapi/boom';
-import { set } from '@elastic/safer-lodash-set';
 import { get } from 'lodash';
+import { set } from '@elastic/safer-lodash-set';
+import { i18n } from '@kbn/i18n';
 import { getClustersStats } from './get_clusters_stats';
 import { flagSupportedClusters } from './flag_supported_clusters';
 import { getMlJobsForCluster } from '../elasticsearch';
@@ -15,7 +16,7 @@ import { getKibanasForClusters } from '../kibana';
 import { getLogstashForClusters } from '../logstash';
 import { getLogstashPipelineIds } from '../logstash/get_pipeline_ids';
 import { getBeatsForClusters } from '../beats';
-import { getClustersSummary } from './get_clusters_summary';
+import { getClustersSummary, EnhancedClusters } from './get_clusters_summary';
 import {
   STANDALONE_CLUSTER_CLUSTER_UUID,
   CODE_PATH_ML,
@@ -26,21 +27,27 @@ import {
   CODE_PATH_BEATS,
   CODE_PATH_APM,
 } from '../../../common/constants';
+
 import { getApmsForClusters } from '../apm/get_apms_for_clusters';
-import { i18n } from '@kbn/i18n';
 import { checkCcrEnabled } from '../elasticsearch/ccr';
 import { fetchStatus } from '../alerts/fetch_status';
 import { getStandaloneClusterDefinition, hasStandaloneClusters } from '../standalone_clusters';
 import { getLogTypes } from '../logs';
 import { isInCodePath } from './is_in_code_path';
+import { LegacyRequest, Cluster } from '../../types';
 
 /**
  * Get all clusters or the cluster associated with {@code clusterUuid} when it is defined.
  */
 export async function getClustersFromRequest(
-  req,
-  indexPatterns,
-  { clusterUuid, start, end, codePaths } = {}
+  req: LegacyRequest,
+  indexPatterns: { [x: string]: string },
+  {
+    clusterUuid,
+    start,
+    end,
+    codePaths,
+  }: { clusterUuid: string; start: number; end: number; codePaths: string[] }
 ) {
   const {
     esIndexPattern,
@@ -54,7 +61,7 @@ export async function getClustersFromRequest(
   const config = req.server.config();
   const isStandaloneCluster = clusterUuid === STANDALONE_CLUSTER_CLUSTER_UUID;
 
-  let clusters = [];
+  let clusters: Cluster[] = [];
 
   if (isStandaloneCluster) {
     clusters.push(getStandaloneClusterDefinition());
@@ -120,7 +127,6 @@ export async function getClustersFromRequest(
       const rulesClient = req.getRulesClient();
       const alertStatus = await fetchStatus(
         rulesClient,
-        req.server.plugins.monitoring.info,
         undefined,
         clusters.map((cluster) => get(cluster, 'elasticsearch.cluster.id', cluster.cluster_uuid))
       );
@@ -139,16 +145,16 @@ export async function getClustersFromRequest(
               list: Object.keys(alertStatus).reduce((accum, alertName) => {
                 const value = alertStatus[alertName];
                 if (value.states && value.states.length) {
-                  accum[alertName] = {
+                  Reflect.set(accum, alertName, {
                     ...value,
                     states: value.states.filter(
                       (state) =>
                         state.state.cluster.clusterUuid ===
                         get(cluster, 'elasticsearch.cluster.id', cluster.cluster_uuid)
                     ),
-                  };
+                  });
                 } else {
-                  accum[alertName] = value;
+                  Reflect.set(accum, alertName, value);
                 }
                 return accum;
               }, {}),
@@ -197,7 +203,7 @@ export async function getClustersFromRequest(
       );
       // withhold LS overview stats until there is at least 1 pipeline
       if (logstash.clusterUuid === clusterUuid && !pipelines.length) {
-        logstash.stats = {};
+        Reflect.set(logstash, 'stats', {});
       }
       set(clusters[clusterIndex], 'logstash', logstash.stats);
     });
@@ -225,18 +231,18 @@ export async function getClustersFromRequest(
         get(cluster, 'elasticsearch.cluster.id', cluster.cluster_uuid) === apm.clusterUuid
     );
     if (clusterIndex >= 0) {
-      const { stats, config } = apm;
-      clusters[clusterIndex].apm = {
+      const { stats, config: apmConfig } = apm;
+      Reflect.set(clusters[clusterIndex], 'apm', {
         ...stats,
-        config,
-      };
+        config: apmConfig,
+      });
     }
   });
 
   // check ccr configuration
   const isCcrEnabled = await checkCcrEnabled(req, esIndexPattern);
 
-  const kibanaUuid = config.get('server.uuid');
+  const kibanaUuid = config.get('server.uuid')!;
 
-  return getClustersSummary(req.server, clusters, kibanaUuid, isCcrEnabled);
+  return getClustersSummary(req.server, clusters as EnhancedClusters[], kibanaUuid, isCcrEnabled);
 }
diff --git a/x-pack/plugins/monitoring/server/lib/cluster/get_clusters_summary.ts b/x-pack/plugins/monitoring/server/lib/cluster/get_clusters_summary.ts
index 955c4d3d3b62..e29c1ad5292f 100644
--- a/x-pack/plugins/monitoring/server/lib/cluster/get_clusters_summary.ts
+++ b/x-pack/plugins/monitoring/server/lib/cluster/get_clusters_summary.ts
@@ -16,7 +16,7 @@ import { calculateOverallStatus } from '../calculate_overall_status';
 // @ts-ignore
 import { MonitoringLicenseError } from '../errors/custom_errors';
 
-type EnhancedClusters = ElasticsearchModifiedSource & {
+export type EnhancedClusters = ElasticsearchModifiedSource & {
   license: ElasticsearchLegacySource['license'];
   [key: string]: any;
 };
diff --git a/x-pack/plugins/monitoring/server/lib/cluster/get_index_patterns.js b/x-pack/plugins/monitoring/server/lib/cluster/get_index_patterns.ts
similarity index 88%
rename from x-pack/plugins/monitoring/server/lib/cluster/get_index_patterns.js
rename to x-pack/plugins/monitoring/server/lib/cluster/get_index_patterns.ts
index 52f2bb7b1973..d908d6180772 100644
--- a/x-pack/plugins/monitoring/server/lib/cluster/get_index_patterns.js
+++ b/x-pack/plugins/monitoring/server/lib/cluster/get_index_patterns.ts
@@ -5,6 +5,7 @@
  * 2.0.
  */
 
+import { LegacyServer } from '../../types';
 import { prefixIndexPattern } from '../ccs_utils';
 import {
   INDEX_PATTERN_ELASTICSEARCH,
@@ -14,7 +15,11 @@ import {
   INDEX_ALERTS,
 } from '../../../common/constants';
 
-export function getIndexPatterns(server, additionalPatterns = {}, ccs = '*') {
+export function getIndexPatterns(
+  server: LegacyServer,
+  additionalPatterns: Record<string, string> = {},
+  ccs: string = '*'
+) {
   const config = server.config();
   const esIndexPattern = prefixIndexPattern(config, INDEX_PATTERN_ELASTICSEARCH, ccs);
   const kbnIndexPattern = prefixIndexPattern(config, INDEX_PATTERN_KIBANA, ccs);
diff --git a/x-pack/plugins/monitoring/server/lib/cluster/is_in_code_path.js b/x-pack/plugins/monitoring/server/lib/cluster/is_in_code_path.ts
similarity index 86%
rename from x-pack/plugins/monitoring/server/lib/cluster/is_in_code_path.js
rename to x-pack/plugins/monitoring/server/lib/cluster/is_in_code_path.ts
index 2b59fb3c460e..2f795e5997f0 100644
--- a/x-pack/plugins/monitoring/server/lib/cluster/is_in_code_path.js
+++ b/x-pack/plugins/monitoring/server/lib/cluster/is_in_code_path.ts
@@ -7,7 +7,7 @@
 
 import { CODE_PATH_ALL } from '../../../common/constants';
 
-export function isInCodePath(codePaths, codePathsToTest) {
+export function isInCodePath(codePaths: string[], codePathsToTest: string[]) {
   if (codePaths.includes(CODE_PATH_ALL)) {
     return true;
   }
diff --git a/x-pack/plugins/monitoring/server/lib/create_query.test.js b/x-pack/plugins/monitoring/server/lib/create_query.test.js
index a1f25d8937b4..60fa6faa79e4 100644
--- a/x-pack/plugins/monitoring/server/lib/create_query.test.js
+++ b/x-pack/plugins/monitoring/server/lib/create_query.test.js
@@ -8,7 +8,7 @@
 import { set } from '@elastic/safer-lodash-set';
 import { MissingRequiredError } from './error_missing_required';
 import { ElasticsearchMetric } from './metrics';
-import { createQuery } from './create_query.js';
+import { createQuery } from './create_query';
 
 let metric;
 
diff --git a/x-pack/plugins/monitoring/server/lib/create_query.js b/x-pack/plugins/monitoring/server/lib/create_query.ts
similarity index 72%
rename from x-pack/plugins/monitoring/server/lib/create_query.js
rename to x-pack/plugins/monitoring/server/lib/create_query.ts
index c9a5ffeca3ce..83817280730f 100644
--- a/x-pack/plugins/monitoring/server/lib/create_query.js
+++ b/x-pack/plugins/monitoring/server/lib/create_query.ts
@@ -5,23 +5,37 @@
  * 2.0.
  */
 
-import { defaults, get } from 'lodash';
-import { MissingRequiredError } from './error_missing_required';
+import { defaults } from 'lodash';
 import moment from 'moment';
+import { MissingRequiredError } from './error_missing_required';
 import { standaloneClusterFilter } from './standalone_clusters';
 import { STANDALONE_CLUSTER_CLUSTER_UUID } from '../../common/constants';
 
-export function createTimeFilter(options) {
+export interface TimerangeFilter {
+  range: {
+    [x: string]: {
+      format: 'epoch_millis';
+      gte?: number;
+      lte?: number;
+    };
+  };
+}
+
+export function createTimeFilter(options: {
+  start?: number;
+  end?: number;
+  metric?: { timestampField: string };
+}) {
   const { start, end } = options;
   if (!start && !end) {
     return null;
   }
 
-  const timestampField = get(options, 'metric.timestampField');
+  const timestampField = options.metric?.timestampField;
   if (!timestampField) {
     throw new MissingRequiredError('metric.timestampField');
   }
-  const timeRangeFilter = {
+  const timeRangeFilter: TimerangeFilter = {
     range: {
       [timestampField]: {
         format: 'epoch_millis',
@@ -50,9 +64,17 @@ export function createTimeFilter(options) {
  * @param {Date} options.end - numeric timestamp (optional)
  * @param {Metric} options.metric - Metric instance or metric fields object @see ElasticsearchMetric.getMetricFields
  */
-export function createQuery(options) {
-  options = defaults(options, { filters: [] });
-  const { type, types, clusterUuid, uuid, filters } = options;
+export function createQuery(options: {
+  type?: string;
+  types?: string[];
+  filters?: any[];
+  clusterUuid: string;
+  uuid?: string;
+  start?: number;
+  end?: number;
+  metric?: { uuidField?: string; timestampField: string };
+}) {
+  const { type, types, clusterUuid, uuid, filters } = defaults(options, { filters: [] });
 
   const isFromStandaloneCluster = clusterUuid === STANDALONE_CLUSTER_CLUSTER_UUID;
 
@@ -63,8 +85,8 @@ export function createQuery(options) {
     typeFilter = {
       bool: {
         should: [
-          ...types.map((type) => ({ term: { type } })),
-          ...types.map((type) => ({ term: { 'metricset.name': type } })),
+          ...types.map((t) => ({ term: { type: t } })),
+          ...types.map((t) => ({ term: { 'metricset.name': t } })),
         ],
       },
     };
@@ -78,23 +100,26 @@ export function createQuery(options) {
   let uuidFilter;
   // options.uuid can be null, for example getting all the clusters
   if (uuid) {
-    const uuidField = get(options, 'metric.uuidField');
+    const uuidField = options.metric?.uuidField;
     if (!uuidField) {
       throw new MissingRequiredError('options.uuid given but options.metric.uuidField is false');
     }
     uuidFilter = { term: { [uuidField]: uuid } };
   }
 
-  const timestampField = get(options, 'metric.timestampField');
+  const timestampField = options.metric?.timestampField;
   if (!timestampField) {
     throw new MissingRequiredError('metric.timestampField');
   }
   const timeRangeFilter = createTimeFilter(options);
 
-  const combinedFilters = [typeFilter, clusterUuidFilter, uuidFilter, ...filters];
-  if (timeRangeFilter) {
-    combinedFilters.push(timeRangeFilter);
-  }
+  const combinedFilters = [
+    typeFilter,
+    clusterUuidFilter,
+    uuidFilter,
+    timeRangeFilter ?? undefined,
+    ...filters,
+  ];
 
   if (isFromStandaloneCluster) {
     combinedFilters.push(standaloneClusterFilter);
diff --git a/x-pack/plugins/monitoring/server/lib/details/get_metrics.js b/x-pack/plugins/monitoring/server/lib/details/get_metrics.ts
similarity index 75%
rename from x-pack/plugins/monitoring/server/lib/details/get_metrics.js
rename to x-pack/plugins/monitoring/server/lib/details/get_metrics.ts
index da0c2e0b3fcd..83bb18169ae1 100644
--- a/x-pack/plugins/monitoring/server/lib/details/get_metrics.js
+++ b/x-pack/plugins/monitoring/server/lib/details/get_metrics.ts
@@ -6,21 +6,23 @@
  */
 
 import moment from 'moment';
-import { isPlainObject } from 'lodash';
 import Bluebird from 'bluebird';
 import { checkParam } from '../error_missing_required';
 import { getSeries } from './get_series';
 import { calculateTimeseriesInterval } from '../calculate_timeseries_interval';
 import { getTimezone } from '../get_timezone';
+import { LegacyRequest } from '../../types';
+
+type Metric = string | { keys: string | string[]; name: string };
 
 export async function getMetrics(
-  req,
-  indexPattern,
-  metricSet = [],
-  filters = [],
+  req: LegacyRequest,
+  indexPattern: string,
+  metricSet: Metric[] = [],
+  filters: Array<Record<string, any>> = [],
   metricOptions = {},
-  numOfBuckets = 0,
-  groupBy = null
+  numOfBuckets: number = 0,
+  groupBy: string | Record<string, any> | null = null
 ) {
   checkParam(indexPattern, 'indexPattern in details/getMetrics');
   checkParam(metricSet, 'metricSet in details/getMetrics');
@@ -29,7 +31,7 @@ export async function getMetrics(
   // TODO: Pass in req parameters as explicit function parameters
   let min = moment.utc(req.payload.timeRange.min).valueOf();
   const max = moment.utc(req.payload.timeRange.max).valueOf();
-  const minIntervalSeconds = config.get('monitoring.ui.min_interval_seconds');
+  const minIntervalSeconds = Number(config.get('monitoring.ui.min_interval_seconds'));
   const bucketSize = calculateTimeseriesInterval(min, max, minIntervalSeconds);
   const timezone = await getTimezone(req);
 
@@ -38,11 +40,11 @@ export async function getMetrics(
     min = max - numOfBuckets * bucketSize * 1000;
   }
 
-  return Bluebird.map(metricSet, (metric) => {
+  return Bluebird.map(metricSet, (metric: Metric) => {
     // metric names match the literal metric name, but they can be supplied in groups or individually
     let metricNames;
 
-    if (isPlainObject(metric)) {
+    if (typeof metric !== 'string') {
       metricNames = metric.keys;
     } else {
       metricNames = [metric];
@@ -57,10 +59,10 @@ export async function getMetrics(
       });
     });
   }).then((rows) => {
-    const data = {};
+    const data: Record<string, any> = {};
     metricSet.forEach((key, index) => {
       // keyName must match the value stored in the html template
-      const keyName = isPlainObject(key) ? key.name : key;
+      const keyName = typeof key === 'string' ? key : key.name;
       data[keyName] = rows[index];
     });
 
diff --git a/x-pack/plugins/monitoring/server/lib/details/get_series.js b/x-pack/plugins/monitoring/server/lib/details/get_series.ts
similarity index 74%
rename from x-pack/plugins/monitoring/server/lib/details/get_series.js
rename to x-pack/plugins/monitoring/server/lib/details/get_series.ts
index d06ff950449d..906c2df29fee 100644
--- a/x-pack/plugins/monitoring/server/lib/details/get_series.js
+++ b/x-pack/plugins/monitoring/server/lib/details/get_series.ts
@@ -7,13 +7,36 @@
 
 import { get } from 'lodash';
 import moment from 'moment';
+import { ElasticsearchResponse } from '../../../common/types/es';
+import { LegacyRequest, Bucket } from '../../types';
 import { checkParam } from '../error_missing_required';
 import { metrics } from '../metrics';
-import { createQuery } from '../create_query.js';
+import { createQuery } from '../create_query';
 import { formatTimestampToDuration } from '../../../common';
 import { NORMALIZED_DERIVATIVE_UNIT, CALCULATE_DURATION_UNTIL } from '../../../common/constants';
 import { formatUTCTimestampForTimezone } from '../format_timezone';
 
+type SeriesBucket = Bucket & { metric_mb_deriv?: { normalized_value: number } };
+
+interface Metric {
+  app: string;
+  derivative: boolean;
+  mbField?: string;
+  aggs: any;
+  getDateHistogramSubAggs?: Function;
+  dateHistogramSubAggs?: any;
+  metricAgg: string;
+  field: string;
+  timestampField: string;
+  calculation: (
+    b: SeriesBucket,
+    key: string,
+    metric: Metric,
+    defaultSizeInSeconds: number
+  ) => number | null;
+  serialize: () => string;
+}
+
 /**
  * Derivative metrics for the first two agg buckets are unusable. For the first bucket, there
  * simply is no derivative metric (as calculating a derivative requires two adjacent buckets). For
@@ -27,12 +50,12 @@ import { formatUTCTimestampForTimezone } from '../format_timezone';
  * @param {int} minInMsSinceEpoch Lower bound of timepicker range, in ms-since-epoch
  * @param {int} bucketSizeInSeconds Size of a single date_histogram bucket, in seconds
  */
-function offsetMinForDerivativeMetric(minInMsSinceEpoch, bucketSizeInSeconds) {
+function offsetMinForDerivativeMetric(minInMsSinceEpoch: number, bucketSizeInSeconds: number) {
   return minInMsSinceEpoch - 2 * bucketSizeInSeconds * 1000;
 }
 
 // Use the metric object as the source of truth on where to find the UUID
-function getUuid(req, metric) {
+function getUuid(req: LegacyRequest, metric: Metric) {
   if (metric.app === 'kibana') {
     return req.params.kibanaUuid;
   } else if (metric.app === 'logstash') {
@@ -42,12 +65,11 @@ function getUuid(req, metric) {
   }
 }
 
-function defaultCalculation(bucket, key) {
-  const mbKey = `metric_mb_deriv.normalized_value`;
-  const legacyValue = get(bucket, key, null);
-  const mbValue = get(bucket, mbKey, null);
+function defaultCalculation(bucket: SeriesBucket, key: string) {
+  const legacyValue: number = get(bucket, key, null);
+  const mbValue = bucket.metric_mb_deriv?.normalized_value ?? null;
   let value;
-  if (!isNaN(mbValue) && mbValue > 0) {
+  if (mbValue !== null && !isNaN(mbValue) && mbValue > 0) {
     value = mbValue;
   } else {
     value = legacyValue;
@@ -60,7 +82,7 @@ function defaultCalculation(bucket, key) {
   return value;
 }
 
-function createMetricAggs(metric) {
+function createMetricAggs(metric: Metric) {
   if (metric.derivative) {
     const mbDerivative = metric.mbField
       ? {
@@ -90,18 +112,20 @@ function createMetricAggs(metric) {
 }
 
 async function fetchSeries(
-  req,
-  indexPattern,
-  metric,
-  metricOptions,
-  groupBy,
-  min,
-  max,
-  bucketSize,
-  filters
+  req: LegacyRequest,
+  indexPattern: string,
+  metric: Metric,
+  metricOptions: any,
+  groupBy: string | Record<string, any> | null,
+  min: string | number,
+  max: string | number,
+  bucketSize: number,
+  filters: Array<Record<string, any>>
 ) {
   // if we're using a derivative metric, offset the min (also @see comment on offsetMinForDerivativeMetric function)
-  const adjustedMin = metric.derivative ? offsetMinForDerivativeMetric(min, bucketSize) : min;
+  const adjustedMin = metric.derivative
+    ? offsetMinForDerivativeMetric(Number(min), bucketSize)
+    : Number(min);
 
   let dateHistogramSubAggs = null;
   if (metric.getDateHistogramSubAggs) {
@@ -118,15 +142,15 @@ async function fetchSeries(
       ...createMetricAggs(metric),
     };
     if (metric.mbField) {
-      dateHistogramSubAggs.metric_mb = {
+      Reflect.set(dateHistogramSubAggs, 'metric_mb', {
         [metric.metricAgg]: {
           field: metric.mbField,
         },
-      };
+      });
     }
   }
 
-  let aggs = {
+  let aggs: any = {
     check: {
       date_histogram: {
         field: metric.timestampField,
@@ -154,7 +178,7 @@ async function fetchSeries(
     body: {
       query: createQuery({
         start: adjustedMin,
-        end: max,
+        end: Number(max),
         metric,
         clusterUuid: req.params.clusterUuid,
         // TODO: Pass in the UUID as an explicit function parameter
@@ -165,10 +189,6 @@ async function fetchSeries(
     },
   };
 
-  if (metric.debug) {
-    console.log('metric.debug', JSON.stringify(params));
-  }
-
   const { callWithRequest } = req.server.plugins.elasticsearch.getCluster('monitoring');
   return await callWithRequest(req, 'search', params);
 }
@@ -180,11 +200,11 @@ async function fetchSeries(
  * @param {String} min Max timestamp for results to exist within.
  * @return {Number} Index position to use for the first bucket. {@code buckets.length} if none should be used.
  */
-function findFirstUsableBucketIndex(buckets, min) {
+function findFirstUsableBucketIndex(buckets: SeriesBucket[], min: string | number) {
   const minInMillis = moment.utc(min).valueOf();
 
   for (let i = 0; i < buckets.length; ++i) {
-    const bucketTime = get(buckets, [i, 'key']);
+    const bucketTime = buckets[i].key;
     const bucketTimeInMillis = moment.utc(bucketTime).valueOf();
 
     // if the bucket start time, without knowing the bucket size, is before the filter time, then it's inherently a partial bucket
@@ -208,11 +228,16 @@ function findFirstUsableBucketIndex(buckets, min) {
  * @param {Number} bucketSizeInMillis Size of a bucket in milliseconds. Set to 0 to allow partial trailing buckets.
  * @return {Number} Index position to use for the last bucket. {@code -1} if none should be used.
  */
-function findLastUsableBucketIndex(buckets, max, firstUsableBucketIndex, bucketSizeInMillis = 0) {
+function findLastUsableBucketIndex(
+  buckets: SeriesBucket[],
+  max: string | number,
+  firstUsableBucketIndex: number,
+  bucketSizeInMillis: number = 0
+) {
   const maxInMillis = moment.utc(max).valueOf();
 
   for (let i = buckets.length - 1; i > firstUsableBucketIndex - 1; --i) {
-    const bucketTime = get(buckets, [i, 'key']);
+    const bucketTime = buckets[i].key;
     const bucketTimeInMillis = moment.utc(bucketTime).valueOf() + bucketSizeInMillis;
 
     if (bucketTimeInMillis <= maxInMillis) {
@@ -224,41 +249,25 @@ function findLastUsableBucketIndex(buckets, max, firstUsableBucketIndex, bucketS
   return -1;
 }
 
-const formatBucketSize = (bucketSizeInSeconds) => {
+const formatBucketSize = (bucketSizeInSeconds: number) => {
   const now = moment();
   const timestamp = moment(now).add(bucketSizeInSeconds, 'seconds'); // clone the `now` object
 
   return formatTimestampToDuration(timestamp, CALCULATE_DURATION_UNTIL, now);
 };
 
-function isObject(value) {
-  return typeof value === 'object' && !!value && !Array.isArray(value);
-}
-
-function countBuckets(data, count = 0) {
-  if (data && data.buckets) {
-    count += data.buckets.length;
-    for (const bucket of data.buckets) {
-      for (const key of Object.keys(bucket)) {
-        if (isObject(bucket[key])) {
-          count = countBuckets(bucket[key], count);
-        }
-      }
-    }
-  } else if (data) {
-    for (const key of Object.keys(data)) {
-      if (isObject(data[key])) {
-        count = countBuckets(data[key], count);
-      }
-    }
-  }
-  return count;
-}
-
-function handleSeries(metric, groupBy, min, max, bucketSizeInSeconds, timezone, response) {
+function handleSeries(
+  metric: Metric,
+  groupBy: string | Record<string, any> | null,
+  min: string | number,
+  max: string | number,
+  bucketSizeInSeconds: number,
+  timezone: string,
+  response: ElasticsearchResponse
+) {
   const { derivative, calculation: customCalculation } = metric;
 
-  function getAggregatedData(buckets) {
+  function getAggregatedData(buckets: SeriesBucket[]) {
     const firstUsableBucketIndex = findFirstUsableBucketIndex(buckets, min);
     const lastUsableBucketIndex = findLastUsableBucketIndex(
       buckets,
@@ -266,20 +275,7 @@ function handleSeries(metric, groupBy, min, max, bucketSizeInSeconds, timezone,
       firstUsableBucketIndex,
       bucketSizeInSeconds * 1000
     );
-    let data = [];
-
-    if (metric.debug) {
-      console.log(
-        `metric.debug field=${metric.field} bucketsCreated: ${countBuckets(
-          get(response, 'aggregations.check')
-        )}`
-      );
-      console.log(`metric.debug`, {
-        bucketsLength: buckets.length,
-        firstUsableBucketIndex,
-        lastUsableBucketIndex,
-      });
-    }
+    let data: Array<[string | number, number | null]> = [];
 
     if (firstUsableBucketIndex <= lastUsableBucketIndex) {
       // map buckets to values for charts
@@ -306,15 +302,17 @@ function handleSeries(metric, groupBy, min, max, bucketSizeInSeconds, timezone,
   }
 
   if (groupBy) {
-    return get(response, 'aggregations.groupBy.buckets', []).map((bucket) => {
-      return {
-        groupedBy: bucket.key,
-        ...getAggregatedData(get(bucket, 'check.buckets', [])),
-      };
-    });
+    return (response?.aggregations?.groupBy?.buckets ?? []).map(
+      (bucket: Bucket & { check: { buckets: SeriesBucket[] } }) => {
+        return {
+          groupedBy: bucket.key,
+          ...getAggregatedData(bucket.check.buckets ?? []),
+        };
+      }
+    );
   }
 
-  return getAggregatedData(get(response, 'aggregations.check.buckets', []));
+  return getAggregatedData(response.aggregations?.check?.buckets ?? []);
 }
 
 /**
@@ -329,13 +327,18 @@ function handleSeries(metric, groupBy, min, max, bucketSizeInSeconds, timezone,
  * @return {Promise} The object response containing the {@code timeRange}, {@code metric}, and {@code data}.
  */
 export async function getSeries(
-  req,
-  indexPattern,
-  metricName,
-  metricOptions,
-  filters,
-  groupBy,
-  { min, max, bucketSize, timezone }
+  req: LegacyRequest,
+  indexPattern: string,
+  metricName: string,
+  metricOptions: Record<string, any>,
+  filters: Array<Record<string, any>>,
+  groupBy: string | Record<string, any> | null,
+  {
+    min,
+    max,
+    bucketSize,
+    timezone,
+  }: { min: string | number; max: string | number; bucketSize: number; timezone: string }
 ) {
   checkParam(indexPattern, 'indexPattern in details/getSeries');
 
diff --git a/x-pack/plugins/monitoring/server/lib/elasticsearch/ccr.ts b/x-pack/plugins/monitoring/server/lib/elasticsearch/ccr.ts
index 482cbd360199..17dc48d0b237 100644
--- a/x-pack/plugins/monitoring/server/lib/elasticsearch/ccr.ts
+++ b/x-pack/plugins/monitoring/server/lib/elasticsearch/ccr.ts
@@ -50,5 +50,5 @@ export async function checkCcrEnabled(req: LegacyRequest, esIndexPattern: string
   const mbCcr = response.hits?.hits[0]?._source?.elasticsearch?.cluster?.stats?.stack?.xpack?.ccr;
   const isEnabled = legacyCcr?.enabled ?? mbCcr?.enabled;
   const isAvailable = legacyCcr?.available ?? mbCcr?.available;
-  return isEnabled && isAvailable;
+  return Boolean(isEnabled && isAvailable);
 }
diff --git a/x-pack/plugins/monitoring/server/lib/elasticsearch/convert_metric_names.js b/x-pack/plugins/monitoring/server/lib/elasticsearch/convert_metric_names.ts
similarity index 78%
rename from x-pack/plugins/monitoring/server/lib/elasticsearch/convert_metric_names.js
rename to x-pack/plugins/monitoring/server/lib/elasticsearch/convert_metric_names.ts
index cd3390416ccc..244f2a14a2ec 100644
--- a/x-pack/plugins/monitoring/server/lib/elasticsearch/convert_metric_names.js
+++ b/x-pack/plugins/monitoring/server/lib/elasticsearch/convert_metric_names.ts
@@ -30,13 +30,13 @@ const CONVERTED_TOKEN = `odh_`;
  * @param string prefix - This is the aggregation name prefix where the rest of the name will be the type of aggregation
  * @param object metricObj The metric aggregation itself
  */
-export function convertMetricNames(prefix, metricObj) {
+export function convertMetricNames(prefix: string, metricObj: Record<string, any>) {
   return Object.entries(metricObj).reduce((newObj, [key, value]) => {
     const newValue = cloneDeep(value);
     if (key.includes('_deriv') && newValue.derivative) {
       newValue.derivative.buckets_path = `${CONVERTED_TOKEN}${prefix}__${newValue.derivative.buckets_path}`;
     }
-    newObj[`${CONVERTED_TOKEN}${prefix}__${key}`] = newValue;
+    Reflect.set(newObj, `${CONVERTED_TOKEN}${prefix}__${key}`, newValue);
     return newObj;
   }, {});
 }
@@ -50,32 +50,36 @@ export function convertMetricNames(prefix, metricObj) {
  *
  * @param object byDateBucketResponse - The response object from the single `date_histogram` bucket
  */
-export function uncovertMetricNames(byDateBucketResponse) {
-  const unconverted = {};
+
+type MetricNameBucket = { key: string; key_as_string: string; doc_count: number } & Record<
+  string,
+  any
+>;
+export function uncovertMetricNames(byDateBucketResponse: { buckets: MetricNameBucket[] }) {
+  const unconverted: Record<string, { buckets: MetricNameBucket[] }> = {};
   for (const metricName of LISTING_METRICS_NAMES) {
     unconverted[metricName] = {
       buckets: byDateBucketResponse.buckets.map((bucket) => {
         const {
-          // eslint-disable-next-line camelcase
+          // eslint-disable-next-line @typescript-eslint/naming-convention
           key_as_string,
-          // eslint-disable-next-line camelcase
           key,
-          // eslint-disable-next-line camelcase
+          // eslint-disable-next-line @typescript-eslint/naming-convention
           doc_count,
           ...rest
         } = bucket;
-        const metrics = Object.entries(rest).reduce((accum, [key, value]) => {
-          if (key.startsWith(`${CONVERTED_TOKEN}${metricName}`)) {
-            const name = key.split('__')[1];
+        const metrics = Object.entries(rest).reduce((accum, [k, value]) => {
+          if (k.startsWith(`${CONVERTED_TOKEN}${metricName}`)) {
+            const name = k.split('__')[1];
             accum[name] = value;
           }
           return accum;
-        }, {});
+        }, {} as Record<string, any>);
 
         return {
-          key_as_string /* eslint-disable-line camelcase */,
+          key_as_string,
           key,
-          doc_count /* eslint-disable-line camelcase */,
+          doc_count,
           ...metrics,
         };
       }),
diff --git a/x-pack/plugins/monitoring/server/lib/elasticsearch/index.js b/x-pack/plugins/monitoring/server/lib/elasticsearch/index.ts
similarity index 100%
rename from x-pack/plugins/monitoring/server/lib/elasticsearch/index.js
rename to x-pack/plugins/monitoring/server/lib/elasticsearch/index.ts
diff --git a/x-pack/plugins/monitoring/server/lib/elasticsearch/indices/get_indices.ts b/x-pack/plugins/monitoring/server/lib/elasticsearch/indices/get_indices.ts
index 0a9993769a6e..a43feb8fc84a 100644
--- a/x-pack/plugins/monitoring/server/lib/elasticsearch/indices/get_indices.ts
+++ b/x-pack/plugins/monitoring/server/lib/elasticsearch/indices/get_indices.ts
@@ -35,10 +35,11 @@ export function handleResponse(
       hit.inner_hits?.earliest?.hits?.hits[0]?._source.elasticsearch?.index;
 
     const rateOptions = {
-      hitTimestamp: hit._source.timestamp ?? hit._source['@timestamp'],
+      hitTimestamp: hit._source.timestamp ?? hit._source['@timestamp'] ?? null,
       earliestHitTimestamp:
         hit.inner_hits?.earliest?.hits?.hits[0]?._source.timestamp ??
-        hit.inner_hits?.earliest?.hits?.hits[0]?._source['@timestamp'],
+        hit.inner_hits?.earliest?.hits?.hits[0]?._source['@timestamp'] ??
+        null,
       timeWindowMin: min,
       timeWindowMax: max,
     };
diff --git a/x-pack/plugins/monitoring/server/lib/elasticsearch/indices/index.js b/x-pack/plugins/monitoring/server/lib/elasticsearch/indices/index.ts
similarity index 100%
rename from x-pack/plugins/monitoring/server/lib/elasticsearch/indices/index.js
rename to x-pack/plugins/monitoring/server/lib/elasticsearch/indices/index.ts
diff --git a/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/calculate_node_type.test.js b/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/calculate_node_type.test.js
index 1e056c19ea9e..d249bc82b938 100644
--- a/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/calculate_node_type.test.js
+++ b/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/calculate_node_type.test.js
@@ -6,7 +6,7 @@
  */
 
 import { set } from '@elastic/safer-lodash-set';
-import { calculateNodeType } from './calculate_node_type.js';
+import { calculateNodeType } from './calculate_node_type';
 
 const masterNodeId = 'def456';
 
diff --git a/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/calculate_node_type.js b/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/calculate_node_type.ts
similarity index 69%
rename from x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/calculate_node_type.js
rename to x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/calculate_node_type.ts
index 4b2bcb4cda43..8fc6084b114d 100644
--- a/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/calculate_node_type.js
+++ b/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/calculate_node_type.ts
@@ -12,16 +12,22 @@
  *  - client only node: --node.data=false --node.master=false
  *  https://www.elastic.co/guide/en/elasticsearch/reference/2.x/modules-node.html
  */
-import { includes, isUndefined } from 'lodash';
+import { isUndefined } from 'lodash';
+import { ElasticsearchLegacySource } from '../../../../common/types/es';
 
-export function calculateNodeType(node, masterNodeId) {
+export type Node = ElasticsearchLegacySource['source_node'] & {
+  attributes?: Record<string, any>;
+  node_ids?: Array<string | boolean | undefined>;
+};
+
+export function calculateNodeType(node: Node, masterNodeId?: string | boolean) {
   const attrs = node.attributes || {};
 
-  function mightBe(attr) {
+  function mightBe(attr?: string) {
     return attr === 'true' || isUndefined(attr);
   }
 
-  function isNot(attr) {
+  function isNot(attr?: string) {
     return attr === 'false';
   }
 
@@ -30,7 +36,7 @@ export function calculateNodeType(node, masterNodeId) {
   if (uuid !== undefined && uuid === masterNodeId) {
     return 'master';
   }
-  if (includes(node.node_ids, masterNodeId)) {
+  if (node.node_ids?.includes(masterNodeId)) {
     return 'master';
   }
   if (isNot(attrs.data) && isNot(attrs.master)) {
diff --git a/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_default_node_from_id.js b/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_default_node_from_id.ts
similarity index 76%
rename from x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_default_node_from_id.js
rename to x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_default_node_from_id.ts
index a0d460234041..047bcf554ddf 100644
--- a/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_default_node_from_id.js
+++ b/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_default_node_from_id.ts
@@ -10,7 +10,7 @@
  * If node information can't be retrieved, we call this function
  * that provides some usable defaults
  */
-export function getDefaultNodeFromId(nodeId) {
+export function getDefaultNodeFromId(nodeId: string) {
   return {
     id: nodeId,
     name: nodeId,
@@ -20,3 +20,7 @@ export function getDefaultNodeFromId(nodeId) {
     attributes: {},
   };
 }
+
+export function isDefaultNode(node: any): node is ReturnType<typeof getDefaultNodeFromId> {
+  return !node.uuid;
+}
diff --git a/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_node_summary.ts b/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_node_summary.ts
index 79c44286717b..aed6b40675e4 100644
--- a/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_node_summary.ts
+++ b/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_node_summary.ts
@@ -5,7 +5,6 @@
  * 2.0.
  */
 
-import { get } from 'lodash';
 import { i18n } from '@kbn/i18n';
 // @ts-ignore
 import { checkParam } from '../../error_missing_required';
@@ -14,7 +13,7 @@ import { createQuery } from '../../create_query';
 // @ts-ignore
 import { ElasticsearchMetric } from '../../metrics';
 // @ts-ignore
-import { getDefaultNodeFromId } from './get_default_node_from_id';
+import { getDefaultNodeFromId, isDefaultNode } from './get_default_node_from_id';
 // @ts-ignore
 import { calculateNodeType } from './calculate_node_type';
 // @ts-ignore
@@ -23,7 +22,6 @@ import {
   ElasticsearchSource,
   ElasticsearchResponse,
   ElasticsearchLegacySource,
-  ElasticsearchMetricbeatNode,
 } from '../../../../common/types/es';
 import { LegacyRequest } from '../../../types';
 
@@ -35,9 +33,9 @@ export function handleResponse(
   return (response: ElasticsearchResponse) => {
     let nodeSummary = {};
     const nodeStatsHits = response.hits?.hits ?? [];
-    const nodes: Array<
-      ElasticsearchLegacySource['source_node'] | ElasticsearchMetricbeatNode
-    > = nodeStatsHits.map((hit) => hit._source.elasticsearch?.node || hit._source.source_node); // using [0] value because query results are sorted desc per timestamp
+    const nodes: Array<ElasticsearchLegacySource['source_node']> = nodeStatsHits.map(
+      (hit) => hit._source.elasticsearch?.node || hit._source.source_node
+    ); // using [0] value because query results are sorted desc per timestamp
     const node = nodes[0] || getDefaultNodeFromId(nodeUuid);
     const sourceStats =
       response.hits?.hits[0]?._source.elasticsearch?.node?.stats ||
@@ -46,7 +44,7 @@ export function handleResponse(
       clusterState && clusterState.nodes ? clusterState.nodes[nodeUuid] : undefined;
     const stats = {
       resolver: nodeUuid,
-      node_ids: nodes.map((_node) => node.id || node.uuid),
+      node_ids: nodes.map((_node) => (isDefaultNode(node) ? node.id : node.id || node.uuid)),
       attributes: node.attributes,
       transport_address: response.hits?.hits[0]?._source.service?.address || node.transport_address,
       name: node.name,
@@ -54,8 +52,8 @@ export function handleResponse(
     };
 
     if (clusterNode) {
-      const _shardStats = get(shardStats, ['nodes', nodeUuid], {});
-      const calculatedNodeType = calculateNodeType(stats, get(clusterState, 'master_node')); // set type for labeling / iconography
+      const _shardStats = shardStats.nodes[nodeUuid] ?? {};
+      const calculatedNodeType = calculateNodeType(stats, clusterState?.master_node); // set type for labeling / iconography
       const { nodeType, nodeTypeLabel, nodeTypeClass } = getNodeTypeClassLabel(
         node,
         calculatedNodeType
diff --git a/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_node_type_class_label.js b/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_node_type_class_label.ts
similarity index 69%
rename from x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_node_type_class_label.js
rename to x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_node_type_class_label.ts
index fb7429d9d79b..c0a4f4ff2a48 100644
--- a/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_node_type_class_label.js
+++ b/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_node_type_class_label.ts
@@ -6,6 +6,10 @@
  */
 
 import { nodeTypeLabel, nodeTypeClass } from './lookups';
+import {
+  ElasticsearchLegacySource,
+  ElasticsearchMetricbeatNode,
+} from '../../../../common/types/es';
 
 /*
  * Note: currently only `node` and `master` are supported due to
@@ -13,8 +17,11 @@ import { nodeTypeLabel, nodeTypeClass } from './lookups';
  * @param {Object} node - a node object from getNodes / getNodeSummary
  * @param {Object} type - the node type calculated from `calculateNodeType`
  */
-export function getNodeTypeClassLabel(node, type) {
-  const nodeType = node.master ? 'master' : type;
+export function getNodeTypeClassLabel(
+  node: ElasticsearchLegacySource['source_node'] | ElasticsearchMetricbeatNode,
+  type: keyof typeof nodeTypeLabel
+) {
+  const nodeType = node && 'master' in node ? 'master' : type;
   const returnObj = {
     nodeType,
     nodeTypeLabel: nodeTypeLabel[nodeType],
diff --git a/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_nodes/get_live_nodes.js b/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_nodes/get_live_nodes.ts
similarity index 84%
rename from x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_nodes/get_live_nodes.js
rename to x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_nodes/get_live_nodes.ts
index 3ae1d87427d2..7bcba822845c 100644
--- a/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_nodes/get_live_nodes.js
+++ b/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_nodes/get_live_nodes.ts
@@ -5,7 +5,9 @@
  * 2.0.
  */
 
-export async function getLivesNodes(req) {
+import { LegacyRequest } from '../../../../types';
+
+export async function getLivesNodes(req: LegacyRequest) {
   const params = {
     path: '/_nodes',
     method: 'GET',
diff --git a/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_nodes/get_metric_aggs.js b/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_nodes/get_metric_aggs.ts
similarity index 96%
rename from x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_nodes/get_metric_aggs.js
rename to x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_nodes/get_metric_aggs.ts
index c34458c30469..ea2940ee1589 100644
--- a/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_nodes/get_metric_aggs.js
+++ b/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_nodes/get_metric_aggs.ts
@@ -18,7 +18,7 @@ import { convertMetricNames } from '../../convert_metric_names';
  * @param {Number} bucketSize: Bucket size in seconds for date histogram interval
  * @return {Object} Aggregation DSL
  */
-export function getMetricAggs(listingMetrics) {
+export function getMetricAggs(listingMetrics: string[]) {
   let aggItems = {};
 
   listingMetrics.forEach((metricName) => {
diff --git a/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_nodes/get_node_ids.js b/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_nodes/get_node_ids.ts
similarity index 86%
rename from x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_nodes/get_node_ids.js
rename to x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_nodes/get_node_ids.ts
index 87781417a07e..03524eebd12e 100644
--- a/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_nodes/get_node_ids.js
+++ b/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_nodes/get_node_ids.ts
@@ -9,8 +9,14 @@ import moment from 'moment';
 import { get } from 'lodash';
 import { ElasticsearchMetric } from '../../../metrics';
 import { createQuery } from '../../../create_query';
+import { LegacyRequest, Bucket } from '../../../../types';
 
-export async function getNodeIds(req, indexPattern, { clusterUuid }, size) {
+export async function getNodeIds(
+  req: LegacyRequest,
+  indexPattern: string,
+  { clusterUuid }: { clusterUuid: string },
+  size: number
+) {
   const start = moment.utc(req.payload.timeRange.min).valueOf();
   const end = moment.utc(req.payload.timeRange.max).valueOf();
 
@@ -55,5 +61,7 @@ export async function getNodeIds(req, indexPattern, { clusterUuid }, size) {
 
   const { callWithRequest } = req.server.plugins.elasticsearch.getCluster('monitoring');
   const response = await callWithRequest(req, 'search', params);
-  return get(response, 'aggregations.composite_data.buckets', []).map((bucket) => bucket.key);
+  return get(response, 'aggregations.composite_data.buckets', []).map(
+    (bucket: Bucket) => bucket.key
+  );
 }
diff --git a/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_nodes/get_nodes.ts b/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_nodes/get_nodes.ts
index 442a2b1b9b9c..0b5c0337e6c4 100644
--- a/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_nodes/get_nodes.ts
+++ b/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_nodes/get_nodes.ts
@@ -6,18 +6,12 @@
  */
 
 import moment from 'moment';
-// @ts-ignore
 import { checkParam } from '../../../error_missing_required';
-// @ts-ignore
 import { createQuery } from '../../../create_query';
-// @ts-ignore
 import { calculateAuto } from '../../../calculate_auto';
-// @ts-ignore
 import { ElasticsearchMetric } from '../../../metrics';
-// @ts-ignore
 import { getMetricAggs } from './get_metric_aggs';
 import { handleResponse } from './handle_response';
-// @ts-ignore
 import { LISTING_METRICS_NAMES, LISTING_METRICS_PATHS } from './nodes_listing_metrics';
 import { LegacyRequest } from '../../../../types';
 import { ElasticsearchModifiedSource } from '../../../../../common/types/es';
@@ -103,7 +97,7 @@ export async function getNodes(
                 min_doc_count: 0,
                 fixed_interval: bucketSize + 's',
               },
-              aggs: getMetricAggs(LISTING_METRICS_NAMES, bucketSize),
+              aggs: getMetricAggs(LISTING_METRICS_NAMES),
             },
           },
         },
diff --git a/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_nodes/get_paginated_nodes.js b/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_nodes/get_paginated_nodes.ts
similarity index 74%
rename from x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_nodes/get_paginated_nodes.js
rename to x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_nodes/get_paginated_nodes.ts
index 485378fd01de..118140fe3f9c 100644
--- a/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_nodes/get_paginated_nodes.js
+++ b/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_nodes/get_paginated_nodes.ts
@@ -5,12 +5,15 @@
  * 2.0.
  */
 
-import { get, isUndefined } from 'lodash';
+import { isUndefined } from 'lodash';
 import { getNodeIds } from './get_node_ids';
+// @ts-ignore
 import { filter } from '../../../pagination/filter';
 import { sortNodes } from './sort_nodes';
+// @ts-ignore
 import { paginate } from '../../../pagination/paginate';
 import { getMetrics } from '../../../details/get_metrics';
+import { LegacyRequest } from '../../../../types';
 
 /**
  * This function performs an optimization around the node listing tables in the UI. To avoid
@@ -28,25 +31,41 @@ import { getMetrics } from '../../../details/get_metrics';
  * @param {*} sort - ({ field, direction })
  * @param {*} queryText - Text that will be used to filter out pipelines
  */
+
+interface Node {
+  name: string;
+  uuid: string;
+  isOnline: boolean;
+  shardCount: number;
+}
+
 export async function getPaginatedNodes(
-  req,
-  esIndexPattern,
-  { clusterUuid },
-  metricSet,
-  pagination,
-  sort,
-  queryText,
-  { clusterStats, nodesShardCount }
+  req: LegacyRequest,
+  esIndexPattern: string,
+  { clusterUuid }: { clusterUuid: string },
+  metricSet: string[],
+  pagination: { index: number; size: number },
+  sort: { field: string; direction: 'asc' | 'desc' },
+  queryText: string,
+  {
+    clusterStats,
+    nodesShardCount,
+  }: {
+    clusterStats: {
+      cluster_state: { nodes: Record<string, Node> };
+    };
+    nodesShardCount: { nodes: Record<string, { shardCount: number }> };
+  }
 ) {
   const config = req.server.config();
-  const size = config.get('monitoring.ui.max_bucket_size');
-  const nodes = await getNodeIds(req, esIndexPattern, { clusterUuid }, size);
+  const size = Number(config.get('monitoring.ui.max_bucket_size'));
+  const nodes: Node[] = await getNodeIds(req, esIndexPattern, { clusterUuid }, size);
 
   // Add `isOnline` and shards from the cluster state and shard stats
-  const clusterState = get(clusterStats, 'cluster_state', { nodes: {} });
+  const clusterState = clusterStats?.cluster_state ?? { nodes: {} };
   for (const node of nodes) {
-    node.isOnline = !isUndefined(get(clusterState, ['nodes', node.uuid]));
-    node.shardCount = get(nodesShardCount, `nodes[${node.uuid}].shardCount`, 0);
+    node.isOnline = !isUndefined(clusterState?.nodes[node.uuid]);
+    node.shardCount = nodesShardCount?.nodes[node.uuid]?.shardCount ?? 0;
   }
 
   // `metricSet` defines a list of metrics that are sortable in the UI
@@ -82,7 +101,7 @@ export async function getPaginatedNodes(
 
     const metricList = metricSeriesData[metricName];
     for (const metricItem of metricList[0]) {
-      const node = nodes.find((node) => node.uuid === metricItem.groupedBy);
+      const node = nodes.find((n) => n.uuid === metricItem.groupedBy);
       if (!node) {
         continue;
       }
@@ -91,7 +110,7 @@ export async function getPaginatedNodes(
       if (dataSeries && dataSeries.length) {
         const lastItem = dataSeries[dataSeries.length - 1];
         if (lastItem.length && lastItem.length === 2) {
-          node[metricName] = lastItem[1];
+          Reflect.set(node, metricName, lastItem[1]);
         }
       }
     }
diff --git a/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_nodes/handle_response.ts b/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_nodes/handle_response.ts
index 5beabe70f077..9fc06f1f9654 100644
--- a/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_nodes/handle_response.ts
+++ b/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_nodes/handle_response.ts
@@ -7,9 +7,7 @@
 
 import { get } from 'lodash';
 import { mapNodesInfo } from './map_nodes_info';
-// @ts-ignore
 import { mapNodesMetrics } from './map_nodes_metrics';
-// @ts-ignore
 import { uncovertMetricNames } from '../../convert_metric_names';
 import { ElasticsearchResponse, ElasticsearchModifiedSource } from '../../../../../common/types/es';
 
@@ -26,7 +24,7 @@ export function handleResponse(
   clusterStats: ElasticsearchModifiedSource | undefined,
   nodesShardCount: { nodes: { [nodeId: string]: { shardCount: number } } } | undefined,
   pageOfNodes: Array<{ uuid: string }>,
-  timeOptions = {}
+  timeOptions: { min?: number; max?: number; bucketSize?: number } = {}
 ) {
   if (!get(response, 'hits.hits')) {
     return [];
diff --git a/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_nodes/index.js b/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_nodes/index.ts
similarity index 100%
rename from x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_nodes/index.js
rename to x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_nodes/index.ts
diff --git a/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_nodes/map_nodes_info.ts b/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_nodes/map_nodes_info.ts
index 745556f5d2c8..aaa2092e08c4 100644
--- a/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_nodes/map_nodes_info.ts
+++ b/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_nodes/map_nodes_info.ts
@@ -6,9 +6,7 @@
  */
 
 import { isUndefined } from 'lodash';
-// @ts-ignore
 import { calculateNodeType } from '../calculate_node_type';
-// @ts-ignore
 import { getNodeTypeClassLabel } from '../get_node_type_class_label';
 import {
   ElasticsearchResponseHit,
@@ -31,6 +29,7 @@ export function mapNodesInfo(
 
   return nodeHits.reduce((prev, node) => {
     const sourceNode = node._source.source_node || node._source.elasticsearch?.node;
+    if (!sourceNode) return prev;
 
     const calculatedNodeType = calculateNodeType(sourceNode, clusterState?.master_node);
     const { nodeType, nodeTypeLabel, nodeTypeClass } = getNodeTypeClassLabel(
diff --git a/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_nodes/map_nodes_metrics.js b/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_nodes/map_nodes_metrics.ts
similarity index 75%
rename from x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_nodes/map_nodes_metrics.js
rename to x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_nodes/map_nodes_metrics.ts
index bee11e0e1049..3426c7ac4264 100644
--- a/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_nodes/map_nodes_metrics.js
+++ b/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_nodes/map_nodes_metrics.ts
@@ -8,8 +8,16 @@
 import { get, map, min, max, last } from 'lodash';
 import { filterPartialBuckets } from '../../../filter_partial_buckets';
 import { metrics } from '../../../metrics';
+import { Bucket } from '../../../../types';
 
-function calcSlope(data) {
+type MetricBucket = Bucket & { metric_deriv?: { value: number; normalized_value: number } };
+interface TimeOptions {
+  min?: number;
+  max?: number;
+  bucketSize?: number;
+}
+
+function calcSlope(data: Array<{ x: number; y: number }>) {
   const length = data.length;
   const xSum = data.reduce((prev, curr) => prev + curr.x, 0);
   const ySum = data.reduce((prev, curr) => prev + curr.y, 0);
@@ -27,12 +35,15 @@ function calcSlope(data) {
   return null; // convert possible NaN to `null` for JSON-friendliness
 }
 
-const mapBuckets = (bucket, metric) => {
+const mapBuckets = (
+  bucket: MetricBucket,
+  metric: { derivative: boolean; calculation: (b: Bucket) => number | null }
+) => {
   const x = bucket.key;
 
   if (metric.calculation) {
     return {
-      x: bucket.key,
+      x: Number(bucket.key),
       y: metric.calculation(bucket),
     };
   }
@@ -60,12 +71,16 @@ const mapBuckets = (bucket, metric) => {
   return { x, y: null };
 };
 
-function reduceMetric(metricName, metricBuckets, { min: startTime, max: endTime, bucketSize }) {
+function reduceMetric(
+  metricName: string,
+  metricBuckets: MetricBucket[],
+  { min: startTime, max: endTime, bucketSize }: TimeOptions
+) {
   if (startTime === undefined || endTime === undefined || startTime >= endTime) {
     return null;
   }
 
-  const partialBucketFilter = filterPartialBuckets(startTime, endTime, bucketSize, {
+  const partialBucketFilter = filterPartialBuckets(startTime, endTime, bucketSize!, {
     ignoreEarly: true,
   });
   const metric = metrics[metricName];
@@ -85,7 +100,7 @@ function reduceMetric(metricName, metricBuckets, { min: startTime, max: endTime,
   const minVal = min(map(mappedData, 'y'));
   const maxVal = max(map(mappedData, 'y'));
   const lastVal = last(map(mappedData, 'y'));
-  const slope = calcSlope(mappedData) > 0 ? 1 : -1; // no need for the entire precision, it's just an up/down arrow
+  const slope = Number(calcSlope(mappedData as Array<{ x: number; y: number }>)) > 0 ? 1 : -1; // no need for the entire precision, it's just an up/down arrow
 
   return {
     metric: metric.serialize(),
@@ -93,14 +108,14 @@ function reduceMetric(metricName, metricBuckets, { min: startTime, max: endTime,
   };
 }
 
-function reduceAllMetrics(metricSet, timeOptions) {
-  const metrics = {};
+function reduceAllMetrics(metricSet: string[], timeOptions: TimeOptions) {
+  const reducedMetrics: Record<string, any> = {};
   Object.keys(metricSet).forEach((metricName) => {
     const metricBuckets = get(metricSet, [metricName, 'buckets']);
-    metrics[metricName] = reduceMetric(metricName, metricBuckets, timeOptions); // append summarized metric data
+    reducedMetrics[metricName] = reduceMetric(metricName, metricBuckets, timeOptions); // append summarized metric data
   });
 
-  return metrics;
+  return reducedMetrics;
 }
 
 /*
@@ -112,8 +127,12 @@ function reduceAllMetrics(metricSet, timeOptions) {
  * @param {Object} timeOptions: min, max, and bucketSize needed for date histogram creation
  * @return {Object} summarized metric data about each node keyed by nodeId
  */
-export function mapNodesMetrics(metricsForNodes, nodesInfo, timeOptions) {
-  const metricRows = {};
+export function mapNodesMetrics(
+  metricsForNodes: Record<string, string[]>,
+  nodesInfo: Record<string, { isOnline: boolean }>,
+  timeOptions: TimeOptions
+) {
+  const metricRows: Record<string, any> = {};
   Object.keys(metricsForNodes).forEach((nodeId) => {
     if (nodesInfo[nodeId].isOnline) {
       // only do the work of mapping metrics if the node is online
diff --git a/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_nodes/nodes_listing_metrics.js b/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_nodes/nodes_listing_metrics.ts
similarity index 100%
rename from x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_nodes/nodes_listing_metrics.js
rename to x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_nodes/nodes_listing_metrics.ts
diff --git a/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_nodes/sort_nodes.js b/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_nodes/sort_nodes.ts
similarity index 76%
rename from x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_nodes/sort_nodes.js
rename to x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_nodes/sort_nodes.ts
index 3a1f9e264a2e..33d29f2a0599 100644
--- a/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_nodes/sort_nodes.js
+++ b/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/get_nodes/sort_nodes.ts
@@ -7,7 +7,9 @@
 
 import { orderBy } from 'lodash';
 
-export function sortNodes(nodes, sort) {
+type Node = Record<string, any>;
+
+export function sortNodes(nodes: Node[], sort?: { field: string; direction: 'asc' | 'desc' }) {
   if (!sort || !sort.field) {
     return nodes;
   }
diff --git a/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/index.js b/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/index.ts
similarity index 88%
rename from x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/index.js
rename to x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/index.ts
index 99ada270ac77..8f474c028484 100644
--- a/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/index.js
+++ b/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/index.ts
@@ -7,6 +7,6 @@
 
 export { getNodes } from './get_nodes';
 export { getNodeSummary } from './get_node_summary';
-export { calculateNodeType } from './calculate_node_type';
+export { calculateNodeType, Node } from './calculate_node_type';
 export { getNodeTypeClassLabel } from './get_node_type_class_label';
 export { getDefaultNodeFromId } from './get_default_node_from_id';
diff --git a/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/lookups.js b/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/lookups.ts
similarity index 100%
rename from x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/lookups.js
rename to x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/lookups.ts
diff --git a/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/types.ts b/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/types.ts
new file mode 100644
index 000000000000..57c0e643888e
--- /dev/null
+++ b/x-pack/plugins/monitoring/server/lib/elasticsearch/nodes/types.ts
@@ -0,0 +1,13 @@
+/*
+ * Copyright Elasticsearch B.V. and/or licensed to Elasticsearch B.V. under one
+ * or more contributor license agreements. Licensed under the Elastic License
+ * 2.0; you may not use this file except in compliance with the Elastic License
+ * 2.0.
+ */
+
+import { ElasticsearchLegacySource } from '../../../../common/types/es';
+
+export type Node = ElasticsearchLegacySource['source_node'] & {
+  attributes?: Record<string, any>;
+  node_ids: Array<string | undefined>;
+};
diff --git a/x-pack/plugins/monitoring/server/lib/elasticsearch/shards/calculate_shard_stat_indices_totals.js b/x-pack/plugins/monitoring/server/lib/elasticsearch/shards/calculate_shard_stat_indices_totals.ts
similarity index 83%
rename from x-pack/plugins/monitoring/server/lib/elasticsearch/shards/calculate_shard_stat_indices_totals.js
rename to x-pack/plugins/monitoring/server/lib/elasticsearch/shards/calculate_shard_stat_indices_totals.ts
index 1b0c4a13cebb..96e7b5491c4d 100644
--- a/x-pack/plugins/monitoring/server/lib/elasticsearch/shards/calculate_shard_stat_indices_totals.js
+++ b/x-pack/plugins/monitoring/server/lib/elasticsearch/shards/calculate_shard_stat_indices_totals.ts
@@ -8,7 +8,16 @@
 /*
  * Calculate totals from mapped indices data
  */
-export function calculateIndicesTotals(indices) {
+export function calculateIndicesTotals(
+  indices: Record<
+    string,
+    {
+      primary: number;
+      replica: number;
+      unassigned: { primary: number; replica: number };
+    }
+  >
+) {
   // create datasets for each index
   const metrics = Object.keys(indices).map((i) => {
     const index = indices[i];
diff --git a/x-pack/plugins/monitoring/server/lib/elasticsearch/shards/get_shard_stat_aggs.js b/x-pack/plugins/monitoring/server/lib/elasticsearch/shards/get_shard_stat_aggs.ts
similarity index 87%
rename from x-pack/plugins/monitoring/server/lib/elasticsearch/shards/get_shard_stat_aggs.js
rename to x-pack/plugins/monitoring/server/lib/elasticsearch/shards/get_shard_stat_aggs.ts
index 8bb79c0b0a70..cf11c939fb23 100644
--- a/x-pack/plugins/monitoring/server/lib/elasticsearch/shards/get_shard_stat_aggs.js
+++ b/x-pack/plugins/monitoring/server/lib/elasticsearch/shards/get_shard_stat_aggs.ts
@@ -9,7 +9,14 @@
  * @param {Object} config - Kibana config service
  * @param {Boolean} includeNodes - whether to add the aggs for node shards
  */
-export function getShardAggs(config, includeNodes, includeIndices) {
+
+import { LegacyServer } from '../../../types';
+
+export function getShardAggs(
+  config: ReturnType<LegacyServer['config']>,
+  includeNodes: boolean,
+  includeIndices: boolean
+) {
   const maxBucketSize = config.get('monitoring.ui.max_bucket_size');
   const aggSize = 10;
   const indicesAgg = {
diff --git a/x-pack/plugins/monitoring/server/lib/elasticsearch/shards/get_unassigned_shards.js b/x-pack/plugins/monitoring/server/lib/elasticsearch/shards/get_unassigned_shards.ts
similarity index 67%
rename from x-pack/plugins/monitoring/server/lib/elasticsearch/shards/get_unassigned_shards.js
rename to x-pack/plugins/monitoring/server/lib/elasticsearch/shards/get_unassigned_shards.ts
index 86e747f41505..12735406ff90 100644
--- a/x-pack/plugins/monitoring/server/lib/elasticsearch/shards/get_unassigned_shards.js
+++ b/x-pack/plugins/monitoring/server/lib/elasticsearch/shards/get_unassigned_shards.ts
@@ -5,18 +5,18 @@
  * 2.0.
  */
 
-import { get } from 'lodash';
-
 // Methods for calculating metrics for
 // - Number of Primary Shards
 // - Number of Replica Shards
 // - Unassigned Primary Shards
 // - Unassigned Replica Shards
-export function getUnassignedShards(indexShardStats) {
+export function getUnassignedShards(indexShardStats: {
+  unassigned: { primary: number; replica: number };
+}) {
   let unassignedShards = 0;
 
-  unassignedShards += get(indexShardStats, 'unassigned.primary');
-  unassignedShards += get(indexShardStats, 'unassigned.replica');
+  unassignedShards += indexShardStats.unassigned.primary;
+  unassignedShards += indexShardStats.unassigned.replica;
 
   return unassignedShards;
 }
diff --git a/x-pack/plugins/monitoring/server/lib/elasticsearch/shards/index.js b/x-pack/plugins/monitoring/server/lib/elasticsearch/shards/index.ts
similarity index 100%
rename from x-pack/plugins/monitoring/server/lib/elasticsearch/shards/index.js
rename to x-pack/plugins/monitoring/server/lib/elasticsearch/shards/index.ts
diff --git a/x-pack/plugins/monitoring/server/lib/elasticsearch/shards/normalize_shard_objects.js b/x-pack/plugins/monitoring/server/lib/elasticsearch/shards/normalize_shard_objects.ts
similarity index 71%
rename from x-pack/plugins/monitoring/server/lib/elasticsearch/shards/normalize_shard_objects.js
rename to x-pack/plugins/monitoring/server/lib/elasticsearch/shards/normalize_shard_objects.ts
index c0bb9836238d..511935f615cd 100644
--- a/x-pack/plugins/monitoring/server/lib/elasticsearch/shards/normalize_shard_objects.js
+++ b/x-pack/plugins/monitoring/server/lib/elasticsearch/shards/normalize_shard_objects.ts
@@ -5,8 +5,8 @@
  * 2.0.
  */
 
-import { get, partition } from 'lodash';
-import { calculateNodeType } from '../nodes';
+import { partition } from 'lodash';
+import { calculateNodeType, Node } from '../nodes';
 
 /*
  * Reducer function for a set of nodes to key the array by nodeId, summarize
@@ -14,8 +14,28 @@ import { calculateNodeType } from '../nodes';
  * @param masterNode = nodeId of master node
  * @return reducer function for set of nodes
  */
-export function normalizeNodeShards(masterNode) {
-  return (nodes, node) => {
+
+type NodeShard = Node & {
+  key: string;
+  node_ids: { buckets: Array<{ key: string }> };
+  node_names: { buckets: Array<{ key: string }> };
+  index_count: { value: number };
+  doc_count: number;
+};
+
+interface ShardBucket {
+  key: string;
+  primary: {
+    buckets: Array<{
+      key: string;
+      key_as_string: string;
+      doc_count: number;
+    }>;
+  };
+}
+
+export function normalizeNodeShards(masterNode: string) {
+  return (nodes: NodeShard[], node: NodeShard) => {
     if (node.key && node.node_ids) {
       const nodeIds = node.node_ids.buckets.map((b) => b.key);
       const _node = {
@@ -27,8 +47,8 @@ export function normalizeNodeShards(masterNode) {
         ...nodes,
         [node.key]: {
           shardCount: node.doc_count,
-          indexCount: get(node, 'index_count.value'),
-          name: get(node, 'node_names.buckets[0].key'),
+          indexCount: node.index_count.value,
+          name: node.node_names.buckets[0].key,
           node_ids: nodeIds,
           type: calculateNodeType(_node, masterNode), // put the "star" icon on the node link in the shard allocator
         },
@@ -38,12 +58,12 @@ export function normalizeNodeShards(masterNode) {
   };
 }
 
-const countShards = (shardBuckets) => {
+const countShards = (shardBuckets: ShardBucket[]) => {
   let primaryShards = 0;
   let replicaShards = 0;
 
   shardBuckets.forEach((shard) => {
-    const primaryMap = get(shard, 'primary.buckets', []);
+    const primaryMap = shard.primary.buckets ?? [];
 
     const primaryBucket = primaryMap.find((b) => b.key_as_string === 'true');
     if (primaryBucket !== undefined) {
@@ -62,13 +82,18 @@ const countShards = (shardBuckets) => {
   };
 };
 
+interface Index {
+  key: string;
+  states?: { buckets?: ShardBucket[] };
+}
+
 /*
  * Reducer function for a set of indices to key the array by index name, and
  * summarize the shard data.
  * @return reducer function for set of indices
  */
-export function normalizeIndexShards(indices, index) {
-  const stateBuckets = get(index, 'states.buckets', []);
+export function normalizeIndexShards(indices: Index[], index: Index) {
+  const stateBuckets = index.states?.buckets ?? [];
   const [assignedShardBuckets, unassignedShardBuckets] = partition(stateBuckets, (b) => {
     return b.key === 'STARTED' || b.key === 'RELOCATING';
   });
diff --git a/x-pack/plugins/monitoring/server/lib/elasticsearch/verify_monitoring_auth.js b/x-pack/plugins/monitoring/server/lib/elasticsearch/verify_monitoring_auth.ts
similarity index 93%
rename from x-pack/plugins/monitoring/server/lib/elasticsearch/verify_monitoring_auth.js
rename to x-pack/plugins/monitoring/server/lib/elasticsearch/verify_monitoring_auth.ts
index e4cee4d4455c..7673f1b7ff05 100644
--- a/x-pack/plugins/monitoring/server/lib/elasticsearch/verify_monitoring_auth.js
+++ b/x-pack/plugins/monitoring/server/lib/elasticsearch/verify_monitoring_auth.ts
@@ -8,6 +8,7 @@
 import { get } from 'lodash';
 import Boom from '@hapi/boom';
 import { INDEX_PATTERN } from '../../../common/constants';
+import { LegacyRequest } from '../../types';
 
 /*
  * Check the currently logged-in user's privileges for "read" privileges on the
@@ -16,7 +17,7 @@ import { INDEX_PATTERN } from '../../../common/constants';
  *
  * @param req {Object} the server route handler request object
  */
-export async function verifyMonitoringAuth(req) {
+export async function verifyMonitoringAuth(req: LegacyRequest) {
   const xpackInfo = get(req.server.plugins.monitoring, 'info');
 
   if (xpackInfo) {
@@ -37,7 +38,7 @@ export async function verifyMonitoringAuth(req) {
  * @param req {Object} the server route handler request object
  * @return {Promise} That either resolves with no response (void) or an exception.
  */
-async function verifyHasPrivileges(req) {
+async function verifyHasPrivileges(req: LegacyRequest) {
   const { callWithRequest } = req.server.plugins.elasticsearch.getCluster('monitoring');
 
   let response;
diff --git a/x-pack/plugins/monitoring/server/lib/error_missing_required.js b/x-pack/plugins/monitoring/server/lib/error_missing_required.ts
similarity index 66%
rename from x-pack/plugins/monitoring/server/lib/error_missing_required.js
rename to x-pack/plugins/monitoring/server/lib/error_missing_required.ts
index b63fecdd56c6..130e3d8a8e30 100644
--- a/x-pack/plugins/monitoring/server/lib/error_missing_required.js
+++ b/x-pack/plugins/monitoring/server/lib/error_missing_required.ts
@@ -10,7 +10,7 @@
  * @param param - anything
  * @param context {String} calling context used in the error message
  */
-export function checkParam(param, context) {
+export function checkParam(param: any, context: string) {
   if (!param) {
     throw new MissingRequiredError(context);
   }
@@ -21,10 +21,12 @@ export function checkParam(param, context) {
  * - verification in unit tests
  * see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error
  */
-export function MissingRequiredError(param) {
-  this.name = 'MissingRequiredError';
-  this.message = `Missing required parameter or field: ${param}`;
-  this.stack = new Error().stack;
+
+export class MissingRequiredError extends Error {
+  constructor(param: string) {
+    super();
+    this.name = 'MissingRequiredError';
+    this.message = `Missing required parameter or field: ${param}`;
+    this.stack = new Error().stack;
+  }
 }
-MissingRequiredError.prototype = Object.create(Error.prototype);
-MissingRequiredError.prototype.constructor = MissingRequiredError;
diff --git a/x-pack/plugins/monitoring/server/lib/filter_partial_buckets.js b/x-pack/plugins/monitoring/server/lib/filter_partial_buckets.ts
similarity index 70%
rename from x-pack/plugins/monitoring/server/lib/filter_partial_buckets.js
rename to x-pack/plugins/monitoring/server/lib/filter_partial_buckets.ts
index c39cfc4ea439..35d079fa323c 100644
--- a/x-pack/plugins/monitoring/server/lib/filter_partial_buckets.js
+++ b/x-pack/plugins/monitoring/server/lib/filter_partial_buckets.ts
@@ -7,22 +7,31 @@
 
 import moment from 'moment';
 
+interface Bucket {
+  key: string;
+}
+
 /* calling .subtract or .add on a moment object mutates the object
  * so this function shortcuts creating a fresh object */
-function getTime(bucket) {
+function getTime(bucket: Bucket) {
   return moment.utc(bucket.key);
 }
 
 /* find the milliseconds of difference between 2 moment objects */
-function getDelta(t1, t2) {
+function getDelta(t1: number, t2: number) {
   return moment.duration(t1 - t2).asMilliseconds();
 }
 
-export function filterPartialBuckets(min, max, bucketSize, options = {}) {
-  return (bucket) => {
+export function filterPartialBuckets(
+  min: number,
+  max: number,
+  bucketSize: number,
+  options: { ignoreEarly?: boolean } = {}
+) {
+  return (bucket: Bucket) => {
     const bucketTime = getTime(bucket);
     // timestamp is too late to be complete
-    if (getDelta(max, bucketTime.add(bucketSize, 'seconds')) < 0) {
+    if (getDelta(max, bucketTime.add(bucketSize, 'seconds').valueOf()) < 0) {
       return false;
     }
 
@@ -32,7 +41,7 @@ export function filterPartialBuckets(min, max, bucketSize, options = {}) {
      * ignoreEarly */
     if (options.ignoreEarly !== true) {
       // timestamp is too early to be complete
-      if (getDelta(bucketTime.subtract(bucketSize, 'seconds'), min) < 0) {
+      if (getDelta(bucketTime.subtract(bucketSize, 'seconds').valueOf(), min) < 0) {
         return false;
       }
     }
diff --git a/x-pack/plugins/monitoring/server/lib/format_timezone.js b/x-pack/plugins/monitoring/server/lib/format_timezone.ts
similarity index 82%
rename from x-pack/plugins/monitoring/server/lib/format_timezone.js
rename to x-pack/plugins/monitoring/server/lib/format_timezone.ts
index 72ee3aed4b51..afcc58550905 100644
--- a/x-pack/plugins/monitoring/server/lib/format_timezone.js
+++ b/x-pack/plugins/monitoring/server/lib/format_timezone.ts
@@ -16,11 +16,11 @@ import moment from 'moment';
  * @param {*} utcTimestamp UTC timestamp
  * @param {*} timezone The timezone to convert into
  */
-export const formatUTCTimestampForTimezone = (utcTimestamp, timezone) => {
+export const formatUTCTimestampForTimezone = (utcTimestamp: string | number, timezone: string) => {
   if (timezone === 'Browser') {
     return utcTimestamp;
   }
   const offsetInMinutes = moment.tz(timezone).utcOffset();
-  const offsetTimestamp = utcTimestamp + offsetInMinutes * 1 * 60 * 1000;
+  const offsetTimestamp = Number(utcTimestamp) + offsetInMinutes * 1 * 60 * 1000;
   return offsetTimestamp;
 };
diff --git a/x-pack/plugins/monitoring/server/lib/get_timezone.js b/x-pack/plugins/monitoring/server/lib/get_timezone.ts
similarity index 76%
rename from x-pack/plugins/monitoring/server/lib/get_timezone.js
rename to x-pack/plugins/monitoring/server/lib/get_timezone.ts
index 76f3dddfa315..307ec4477bba 100644
--- a/x-pack/plugins/monitoring/server/lib/get_timezone.js
+++ b/x-pack/plugins/monitoring/server/lib/get_timezone.ts
@@ -5,6 +5,8 @@
  * 2.0.
  */
 
-export async function getTimezone(req) {
+import { LegacyRequest } from '../types';
+
+export async function getTimezone(req: LegacyRequest) {
   return await req.getUiSettingsService().get('dateFormat:tz');
 }
diff --git a/x-pack/plugins/monitoring/server/lib/helpers.js b/x-pack/plugins/monitoring/server/lib/helpers.ts
similarity index 79%
rename from x-pack/plugins/monitoring/server/lib/helpers.js
rename to x-pack/plugins/monitoring/server/lib/helpers.ts
index d5ceb2128c28..a904f8cfa497 100644
--- a/x-pack/plugins/monitoring/server/lib/helpers.js
+++ b/x-pack/plugins/monitoring/server/lib/helpers.ts
@@ -5,6 +5,8 @@
  * 2.0.
  */
 
+import { ElasticsearchResponse, ElasticsearchResponseHit } from '../../common/types/es';
+
 export const response = {
   hits: {
     hits: [
@@ -83,20 +85,22 @@ export const response = {
   },
 };
 
-export const defaultResponseSort = (handleResponse) => {
-  const responseMulti = { hits: { hits: [] } };
+export const defaultResponseSort = (
+  handleResponse: (r: ElasticsearchResponse, n1: number, n2: number) => any
+) => {
+  const responseMulti = { hits: { hits: [] as ElasticsearchResponseHit[] } };
   const hit = response.hits.hits[0];
   const version = ['6.6.2', '7.0.0-rc1', '6.7.1'];
 
   for (let i = 0, l = version.length; i < l; ++i) {
     // Deep clone the object to preserve the original
-    const newBeat = JSON.parse(JSON.stringify({ ...hit }));
+    const newBeat: ElasticsearchResponseHit = JSON.parse(JSON.stringify({ ...hit }));
     const { beats_stats: beatsStats } = newBeat._source;
-    beatsStats.timestamp = `2019-01-0${i + 1}T05:00:00.000Z`;
-    beatsStats.beat.version = version[i];
-    beatsStats.beat.uuid = `${i}${beatsStats.beat.uuid}`;
+    beatsStats!.timestamp = `2019-01-0${i + 1}T05:00:00.000Z`;
+    beatsStats!.beat!.version = version[i];
+    beatsStats!.beat!.uuid = `${i}${beatsStats!.beat!.uuid}`;
     responseMulti.hits.hits.push(newBeat);
   }
 
-  return { beats: handleResponse(responseMulti, 0, 0), version };
+  return { beats: handleResponse(responseMulti as ElasticsearchResponse, 0, 0), version };
 };
diff --git a/x-pack/plugins/monitoring/server/lib/kibana/get_kibana_info.ts b/x-pack/plugins/monitoring/server/lib/kibana/get_kibana_info.ts
index 15cc9904dd06..2fa0b02e0fb1 100644
--- a/x-pack/plugins/monitoring/server/lib/kibana/get_kibana_info.ts
+++ b/x-pack/plugins/monitoring/server/lib/kibana/get_kibana_info.ts
@@ -7,7 +7,7 @@
 
 import { merge } from 'lodash';
 // @ts-ignore
-import { checkParam } from '../error_missing_required';
+import { checkParam, MissingRequiredError } from '../error_missing_required';
 // @ts-ignore
 import { calculateAvailability } from '../calculate_availability';
 import { LegacyRequest } from '../../types';
@@ -17,10 +17,13 @@ export function handleResponse(resp: ElasticsearchResponse) {
   const legacySource = resp.hits?.hits[0]?._source.kibana_stats;
   const mbSource = resp.hits?.hits[0]?._source.kibana?.stats;
   const kibana = resp.hits?.hits[0]?._source.kibana?.kibana ?? legacySource?.kibana;
+  const availabilityTimestamp =
+    resp.hits?.hits[0]?._source['@timestamp'] ?? legacySource?.timestamp;
+  if (!availabilityTimestamp) {
+    throw new MissingRequiredError('timestamp');
+  }
   return merge(kibana, {
-    availability: calculateAvailability(
-      resp.hits?.hits[0]?._source['@timestamp'] ?? legacySource?.timestamp
-    ),
+    availability: calculateAvailability(availabilityTimestamp),
     os_memory_free: mbSource?.os?.memory?.free_in_bytes ?? legacySource?.os?.memory?.free_in_bytes,
     uptime: mbSource?.process?.uptime?.ms ?? legacySource?.process?.uptime_in_millis,
   });
diff --git a/x-pack/plugins/monitoring/server/lib/kibana/get_kibanas_for_clusters.js b/x-pack/plugins/monitoring/server/lib/kibana/get_kibanas_for_clusters.ts
similarity index 86%
rename from x-pack/plugins/monitoring/server/lib/kibana/get_kibanas_for_clusters.js
rename to x-pack/plugins/monitoring/server/lib/kibana/get_kibanas_for_clusters.ts
index 141596ffd2f6..4e806c07ee66 100644
--- a/x-pack/plugins/monitoring/server/lib/kibana/get_kibanas_for_clusters.js
+++ b/x-pack/plugins/monitoring/server/lib/kibana/get_kibanas_for_clusters.ts
@@ -6,9 +6,10 @@
  */
 
 import Bluebird from 'bluebird';
-import { chain, find, get } from 'lodash';
+import { chain, find } from 'lodash';
+import { LegacyRequest, Cluster, Bucket } from '../../types';
 import { checkParam } from '../error_missing_required';
-import { createQuery } from '../create_query.js';
+import { createQuery } from '../create_query';
 import { KibanaClusterMetric } from '../metrics';
 
 /*
@@ -24,7 +25,11 @@ import { KibanaClusterMetric } from '../metrics';
  *  - number of instances
  *  - combined health
  */
-export function getKibanasForClusters(req, kbnIndexPattern, clusters) {
+export function getKibanasForClusters(
+  req: LegacyRequest,
+  kbnIndexPattern: string,
+  clusters: Cluster[]
+) {
   checkParam(kbnIndexPattern, 'kbnIndexPattern in kibana/getKibanasForClusters');
 
   const config = req.server.config();
@@ -32,7 +37,7 @@ export function getKibanasForClusters(req, kbnIndexPattern, clusters) {
   const end = req.payload.timeRange.max;
 
   return Bluebird.map(clusters, (cluster) => {
-    const clusterUuid = get(cluster, 'elasticsearch.cluster.id', cluster.cluster_uuid);
+    const clusterUuid = cluster.elasticsearch?.cluster?.id ?? cluster.cluster_uuid;
     const metric = KibanaClusterMetric.getMetricFields();
     const params = {
       index: kbnIndexPattern,
@@ -162,9 +167,9 @@ export function getKibanasForClusters(req, kbnIndexPattern, clusters) {
 
     const { callWithRequest } = req.server.plugins.elasticsearch.getCluster('monitoring');
     return callWithRequest(req, 'search', params).then((result) => {
-      const aggregations = get(result, 'aggregations', {});
-      const kibanaUuids = get(aggregations, 'kibana_uuids.buckets', []);
-      const statusBuckets = get(aggregations, 'status.buckets', []);
+      const aggregations = result.aggregations ?? {};
+      const kibanaUuids = aggregations.kibana_uuids?.buckets ?? [];
+      const statusBuckets = aggregations.status?.buckets ?? [];
 
       // everything is initialized such that it won't impact any rollup
       let status = null;
@@ -185,19 +190,19 @@ export function getKibanasForClusters(req, kbnIndexPattern, clusters) {
           statusBuckets,
           (bucket) => bucket.max_timestamp.value === latestTimestamp
         );
-        status = get(latestBucket, 'key');
+        status = latestBucket.key;
 
-        requestsTotal = get(aggregations, 'requests_total.value');
-        connections = get(aggregations, 'concurrent_connections.value');
-        responseTime = get(aggregations, 'response_time_max.value');
-        memorySize = get(aggregations, 'memory_rss.value'); // resident set size
-        memoryLimit = get(aggregations, 'memory_heap_size_limit.value'); // max old space
+        requestsTotal = aggregations.requests_total?.value;
+        connections = aggregations.concurrent_connections?.value;
+        responseTime = aggregations.response_time_max?.value;
+        memorySize = aggregations.memory_rss?.value;
+        memoryLimit = aggregations.memory_heap_size_limit?.value;
       }
 
       return {
         clusterUuid,
         stats: {
-          uuids: get(aggregations, 'kibana_uuids.buckets', []).map(({ key }) => key),
+          uuids: kibanaUuids.map(({ key }: Bucket) => key),
           status,
           requests_total: requestsTotal,
           concurrent_connections: connections,
diff --git a/x-pack/plugins/monitoring/server/lib/kibana/index.js b/x-pack/plugins/monitoring/server/lib/kibana/index.ts
similarity index 100%
rename from x-pack/plugins/monitoring/server/lib/kibana/index.js
rename to x-pack/plugins/monitoring/server/lib/kibana/index.ts
diff --git a/x-pack/plugins/monitoring/server/lib/logs/detect_reason.js b/x-pack/plugins/monitoring/server/lib/logs/detect_reason.ts
similarity index 75%
rename from x-pack/plugins/monitoring/server/lib/logs/detect_reason.js
rename to x-pack/plugins/monitoring/server/lib/logs/detect_reason.ts
index a739a8d062c3..216d29d841a8 100644
--- a/x-pack/plugins/monitoring/server/lib/logs/detect_reason.js
+++ b/x-pack/plugins/monitoring/server/lib/logs/detect_reason.ts
@@ -5,13 +5,21 @@
  * 2.0.
  */
 
+import { LegacyRequest } from '../../types';
 import { createTimeFilter } from '../create_query';
-import { get } from 'lodash';
+
+interface Opts {
+  start: number;
+  end: number;
+  clusterUuid?: string;
+  nodeUuid?: string;
+  indexUuid?: string;
+}
 
 async function doesFilebeatIndexExist(
-  req,
-  filebeatIndexPattern,
-  { start, end, clusterUuid, nodeUuid, indexUuid }
+  req: LegacyRequest,
+  filebeatIndexPattern: string,
+  { start, end, clusterUuid, nodeUuid, indexUuid }: Opts
 ) {
   const metric = { timestampField: '@timestamp' };
   const filter = [createTimeFilter({ start, end, metric })];
@@ -122,18 +130,18 @@ async function doesFilebeatIndexExist(
   } = await callWithRequest(req, 'msearch', { body });
 
   return {
-    indexPatternExists: get(indexPatternExistsResponse, 'hits.total.value', 0) > 0,
+    indexPatternExists: (indexPatternExistsResponse?.hits?.total.value ?? 0) > 0,
     indexPatternInTimeRangeExists:
-      get(indexPatternExistsInTimeRangeResponse, 'hits.total.value', 0) > 0,
-    typeExistsAtAnyTime: get(typeExistsAtAnyTimeResponse, 'hits.total.value', 0) > 0,
-    typeExists: get(typeExistsResponse, 'hits.total.value', 0) > 0,
-    usingStructuredLogs: get(usingStructuredLogsResponse, 'hits.total.value', 0) > 0,
-    clusterExists: clusterUuid ? get(clusterExistsResponse, 'hits.total.value', 0) > 0 : null,
-    nodeExists: nodeUuid ? get(nodeExistsResponse, 'hits.total.value', 0) > 0 : null,
-    indexExists: indexUuid ? get(indexExistsResponse, 'hits.total.value', 0) > 0 : null,
+      (indexPatternExistsInTimeRangeResponse?.hits?.total.value ?? 0) > 0,
+    typeExistsAtAnyTime: (typeExistsAtAnyTimeResponse?.hits?.total.value ?? 0) > 0,
+    typeExists: (typeExistsResponse?.hits?.total.value ?? 0) > 0,
+    usingStructuredLogs: (usingStructuredLogsResponse?.hits?.total.value ?? 0) > 0,
+    clusterExists: clusterUuid ? (clusterExistsResponse?.hits?.total.value ?? 0) > 0 : null,
+    nodeExists: nodeUuid ? (nodeExistsResponse?.hits?.total.value ?? 0) > 0 : null,
+    indexExists: indexUuid ? (indexExistsResponse?.hits?.total.value ?? 0) > 0 : null,
   };
 }
 
-export async function detectReason(req, filebeatIndexPattern, opts) {
+export async function detectReason(req: LegacyRequest, filebeatIndexPattern: string, opts: Opts) {
   return await doesFilebeatIndexExist(req, filebeatIndexPattern, opts);
 }
diff --git a/x-pack/plugins/monitoring/server/lib/logs/detect_reason_from_exception.js b/x-pack/plugins/monitoring/server/lib/logs/detect_reason_from_exception.ts
similarity index 86%
rename from x-pack/plugins/monitoring/server/lib/logs/detect_reason_from_exception.js
rename to x-pack/plugins/monitoring/server/lib/logs/detect_reason_from_exception.ts
index bd4776409299..6d6ebf9b8dad 100644
--- a/x-pack/plugins/monitoring/server/lib/logs/detect_reason_from_exception.js
+++ b/x-pack/plugins/monitoring/server/lib/logs/detect_reason_from_exception.ts
@@ -5,7 +5,7 @@
  * 2.0.
  */
 
-export function detectReasonFromException(exception) {
+export function detectReasonFromException(exception: Error & { status: number }) {
   const reason = { correctIndexName: true };
 
   if (exception) {
diff --git a/x-pack/plugins/monitoring/server/lib/logs/get_log_types.ts b/x-pack/plugins/monitoring/server/lib/logs/get_log_types.ts
index bbb48c43033d..2346fdd6f453 100644
--- a/x-pack/plugins/monitoring/server/lib/logs/get_log_types.ts
+++ b/x-pack/plugins/monitoring/server/lib/logs/get_log_types.ts
@@ -5,13 +5,9 @@
  * 2.0.
  */
 
-// @ts-ignore
 import { checkParam } from '../error_missing_required';
-// @ts-ignore
-import { createTimeFilter } from '../create_query';
-// @ts-ignore
+import { createTimeFilter, TimerangeFilter } from '../create_query';
 import { detectReason } from './detect_reason';
-// @ts-ignore
 import { detectReasonFromException } from './detect_reason_from_exception';
 import { LegacyRequest } from '../../types';
 import { FilebeatResponse } from '../../../common/types/filebeat';
@@ -25,7 +21,7 @@ async function handleResponse(
   response: FilebeatResponse,
   req: LegacyRequest,
   filebeatIndexPattern: string,
-  opts: { clusterUuid: string; nodeUuid: string; indexUuid: string; start: number; end: number }
+  opts: { clusterUuid?: string; nodeUuid?: string; indexUuid?: string; start: number; end: number }
 ) {
   const result: { enabled: boolean; types: LogType[]; reason?: any } = {
     enabled: false,
@@ -62,12 +58,12 @@ export async function getLogTypes(
     indexUuid,
     start,
     end,
-  }: { clusterUuid: string; nodeUuid: string; indexUuid: string; start: number; end: number }
+  }: { clusterUuid?: string; nodeUuid?: string; indexUuid?: string; start: number; end: number }
 ) {
   checkParam(filebeatIndexPattern, 'filebeatIndexPattern in logs/getLogTypes');
 
   const metric = { timestampField: '@timestamp' };
-  const filter = [
+  const filter: Array<{ term: { [x: string]: string } } | TimerangeFilter | null> = [
     { term: { 'service.type': 'elasticsearch' } },
     createTimeFilter({ start, end, metric }),
   ];
diff --git a/x-pack/plugins/monitoring/server/lib/logs/get_logs.ts b/x-pack/plugins/monitoring/server/lib/logs/get_logs.ts
index 4c21422a5d0c..5226c04377ff 100644
--- a/x-pack/plugins/monitoring/server/lib/logs/get_logs.ts
+++ b/x-pack/plugins/monitoring/server/lib/logs/get_logs.ts
@@ -22,7 +22,7 @@ import { LegacyRequest } from '../../types';
 import { FilebeatResponse } from '../../../common/types/filebeat';
 
 interface Log {
-  timestamp?: string;
+  timestamp?: string | number;
   component?: string;
   node?: string;
   index?: string;
@@ -83,7 +83,7 @@ export async function getLogs(
   checkParam(filebeatIndexPattern, 'filebeatIndexPattern in logs/getLogs');
 
   const metric = { timestampField: '@timestamp' };
-  const filter = [
+  const filter: any[] = [
     { term: { 'service.type': 'elasticsearch' } },
     createTimeFilter({ start, end, metric }),
   ];
diff --git a/x-pack/plugins/monitoring/server/lib/logs/index.js b/x-pack/plugins/monitoring/server/lib/logs/index.ts
similarity index 100%
rename from x-pack/plugins/monitoring/server/lib/logs/index.js
rename to x-pack/plugins/monitoring/server/lib/logs/index.ts
diff --git a/x-pack/plugins/monitoring/server/lib/logstash/get_logstash_for_clusters.js b/x-pack/plugins/monitoring/server/lib/logstash/get_logstash_for_clusters.ts
similarity index 94%
rename from x-pack/plugins/monitoring/server/lib/logstash/get_logstash_for_clusters.js
rename to x-pack/plugins/monitoring/server/lib/logstash/get_logstash_for_clusters.ts
index 17f76834b333..c0c29756818e 100644
--- a/x-pack/plugins/monitoring/server/lib/logstash/get_logstash_for_clusters.js
+++ b/x-pack/plugins/monitoring/server/lib/logstash/get_logstash_for_clusters.ts
@@ -7,14 +7,15 @@
 
 import Bluebird from 'bluebird';
 import { get } from 'lodash';
-import { checkParam } from '../error_missing_required';
-import { createQuery } from '../create_query.js';
-import { LogstashClusterMetric } from '../metrics';
+import { LegacyRequest, Cluster, Bucket } from '../../types';
 import { LOGSTASH } from '../../../common/constants';
+import { checkParam } from '../error_missing_required';
+import { createQuery } from '../create_query';
+import { LogstashClusterMetric } from '../metrics';
 
 const { MEMORY, PERSISTED } = LOGSTASH.QUEUE_TYPES;
 
-const getQueueTypes = (queueBuckets) => {
+const getQueueTypes = (queueBuckets: Array<Bucket & { num_pipelines: { value: number } }>) => {
   const memory = queueBuckets.find((bucket) => bucket.key === MEMORY);
   const persisted = queueBuckets.find((bucket) => bucket.key === PERSISTED);
   return {
@@ -36,7 +37,11 @@ const getQueueTypes = (queueBuckets) => {
  *  - number of instances
  *  - combined health
  */
-export function getLogstashForClusters(req, lsIndexPattern, clusters) {
+export function getLogstashForClusters(
+  req: LegacyRequest,
+  lsIndexPattern: string,
+  clusters: Cluster[]
+) {
   checkParam(lsIndexPattern, 'lsIndexPattern in logstash/getLogstashForClusters');
 
   const start = req.payload.timeRange.min;
@@ -226,7 +231,7 @@ export function getLogstashForClusters(req, lsIndexPattern, clusters) {
 
       let types = get(aggregations, 'pipelines_nested_mb.queue_types.buckets', []);
       if (!types || types.length === 0) {
-        types = get(aggregations, 'pipelines_nested.queue_types.buckets', []);
+        types = aggregations.pipelines_nested?.queue_types.buckets ?? [];
       }
 
       return {
@@ -242,7 +247,7 @@ export function getLogstashForClusters(req, lsIndexPattern, clusters) {
             get(aggregations, 'pipelines_nested_mb.pipelines.value') ||
             get(aggregations, 'pipelines_nested.pipelines.value', 0),
           queue_types: getQueueTypes(types),
-          versions: logstashVersions.map((versionBucket) => versionBucket.key),
+          versions: logstashVersions.map((versionBucket: Bucket) => versionBucket.key),
         },
       };
     });
diff --git a/x-pack/plugins/monitoring/server/lib/logstash/get_node_info.ts b/x-pack/plugins/monitoring/server/lib/logstash/get_node_info.ts
index d047729a0b3c..276b8b119bba 100644
--- a/x-pack/plugins/monitoring/server/lib/logstash/get_node_info.ts
+++ b/x-pack/plugins/monitoring/server/lib/logstash/get_node_info.ts
@@ -7,7 +7,7 @@
 
 import { merge } from 'lodash';
 // @ts-ignore
-import { checkParam } from '../error_missing_required';
+import { checkParam, MissingRequiredError } from '../error_missing_required';
 // @ts-ignore
 import { calculateAvailability } from '../calculate_availability';
 import { LegacyRequest } from '../../types';
@@ -20,8 +20,12 @@ export function handleResponse(resp: ElasticsearchResponse) {
   const legacyStats = resp.hits?.hits[0]?._source?.logstash_stats;
   const mbStats = resp.hits?.hits[0]?._source?.logstash?.node?.stats;
   const logstash = mbStats?.logstash ?? legacyStats?.logstash;
+  const availabilityTimestamp = mbStats?.timestamp ?? legacyStats?.timestamp;
+  if (!availabilityTimestamp) {
+    throw new MissingRequiredError('timestamp');
+  }
   const info = merge(logstash, {
-    availability: calculateAvailability(mbStats?.timestamp ?? legacyStats?.timestamp),
+    availability: calculateAvailability(availabilityTimestamp),
     events: mbStats?.events ?? legacyStats?.events,
     reloads: mbStats?.reloads ?? legacyStats?.reloads,
     queue_type: mbStats?.queue?.type ?? legacyStats?.queue?.type,
diff --git a/x-pack/plugins/monitoring/server/lib/logstash/get_pipeline.ts b/x-pack/plugins/monitoring/server/lib/logstash/get_pipeline.ts
index b17f7d27c6c9..d8bfd91a4aec 100644
--- a/x-pack/plugins/monitoring/server/lib/logstash/get_pipeline.ts
+++ b/x-pack/plugins/monitoring/server/lib/logstash/get_pipeline.ts
@@ -132,9 +132,9 @@ export async function getPipeline(
   // Determine metrics' timeseries interval based on version's timespan
   const minIntervalSeconds = config.get('monitoring.ui.min_interval_seconds');
   const timeseriesInterval = calculateTimeseriesInterval(
-    version.firstSeen,
-    version.lastSeen,
-    minIntervalSeconds
+    Number(version.firstSeen),
+    Number(version.lastSeen),
+    Number(minIntervalSeconds)
   );
 
   const [stateDocument, statsAggregation] = await Promise.all([
diff --git a/x-pack/plugins/monitoring/server/lib/logstash/get_pipeline_ids.js b/x-pack/plugins/monitoring/server/lib/logstash/get_pipeline_ids.ts
similarity index 90%
rename from x-pack/plugins/monitoring/server/lib/logstash/get_pipeline_ids.js
rename to x-pack/plugins/monitoring/server/lib/logstash/get_pipeline_ids.ts
index 2846a968bfed..1a5595d45ffb 100644
--- a/x-pack/plugins/monitoring/server/lib/logstash/get_pipeline_ids.js
+++ b/x-pack/plugins/monitoring/server/lib/logstash/get_pipeline_ids.ts
@@ -7,14 +7,15 @@
 
 import moment from 'moment';
 import { get } from 'lodash';
+import { LegacyRequest, Bucket } from '../../types';
 import { createQuery } from '../create_query';
 import { LogstashMetric } from '../metrics';
 
 export async function getLogstashPipelineIds(
-  req,
-  logstashIndexPattern,
-  { clusterUuid, logstashUuid },
-  size
+  req: LegacyRequest,
+  logstashIndexPattern: string,
+  { clusterUuid, logstashUuid }: { clusterUuid: string; logstashUuid?: string },
+  size: number
 ) {
   const start = moment.utc(req.payload.timeRange.min).valueOf();
   const end = moment.utc(req.payload.timeRange.max).valueOf();
@@ -100,14 +101,14 @@ export async function getLogstashPipelineIds(
   if (!buckets || buckets.length === 0) {
     buckets = get(response, 'aggregations.nest.id.buckets', []);
   }
-  return buckets.map((bucket) => {
+  return buckets.map((bucket: Bucket) => {
     let nodeBuckets = get(bucket, 'unnest_mb.nodes.buckets', []);
     if (!nodeBuckets || nodeBuckets.length === 0) {
       nodeBuckets = get(bucket, 'unnest.nodes.buckets', []);
     }
     return {
       id: bucket.key,
-      nodeIds: nodeBuckets.map((item) => item.key),
+      nodeIds: nodeBuckets.map((item: Bucket) => item.key),
     };
   });
 }
diff --git a/x-pack/plugins/monitoring/server/lib/logstash/get_pipeline_vertex.ts b/x-pack/plugins/monitoring/server/lib/logstash/get_pipeline_vertex.ts
index 3d657e8344e3..e41eea0bce64 100644
--- a/x-pack/plugins/monitoring/server/lib/logstash/get_pipeline_vertex.ts
+++ b/x-pack/plugins/monitoring/server/lib/logstash/get_pipeline_vertex.ts
@@ -150,9 +150,9 @@ export async function getPipelineVertex(
   // Determine metrics' timeseries interval based on version's timespan
   const minIntervalSeconds = config.get('monitoring.ui.min_interval_seconds');
   const timeseriesInterval = calculateTimeseriesInterval(
-    version.firstSeen,
-    version.lastSeen,
-    minIntervalSeconds
+    Number(version.firstSeen),
+    Number(version.lastSeen),
+    Number(minIntervalSeconds)
   );
 
   const [stateDocument, statsAggregation] = await Promise.all([
diff --git a/x-pack/plugins/monitoring/server/lib/logstash/index.js b/x-pack/plugins/monitoring/server/lib/logstash/index.ts
similarity index 100%
rename from x-pack/plugins/monitoring/server/lib/logstash/index.js
rename to x-pack/plugins/monitoring/server/lib/logstash/index.ts
diff --git a/x-pack/plugins/monitoring/server/lib/metrics/apm/classes.js b/x-pack/plugins/monitoring/server/lib/metrics/apm/classes.ts
similarity index 91%
rename from x-pack/plugins/monitoring/server/lib/metrics/apm/classes.js
rename to x-pack/plugins/monitoring/server/lib/metrics/apm/classes.ts
index 638d14594699..4a97e7823999 100644
--- a/x-pack/plugins/monitoring/server/lib/metrics/apm/classes.js
+++ b/x-pack/plugins/monitoring/server/lib/metrics/apm/classes.ts
@@ -5,12 +5,16 @@
  * 2.0.
  */
 
+/* eslint-disable max-classes-per-file */
+
+import { i18n } from '@kbn/i18n';
+// @ts-ignore
 import { ClusterMetric, Metric } from '../classes';
 import { SMALL_FLOAT, LARGE_FLOAT } from '../../../../common/formatting';
-import { i18n } from '@kbn/i18n';
 import { NORMALIZED_DERIVATIVE_UNIT } from '../../../../common/constants';
 
 export class ApmClusterMetric extends ClusterMetric {
+  // @ts-ignore
   constructor(opts) {
     super({
       ...opts,
@@ -28,6 +32,7 @@ export class ApmClusterMetric extends ClusterMetric {
 }
 
 export class ApmMetric extends Metric {
+  // @ts-ignore
   constructor(opts) {
     super({
       ...opts,
@@ -44,7 +49,10 @@ export class ApmMetric extends Metric {
   }
 }
 
+export type ApmMetricFields = ReturnType<typeof ApmMetric.getMetricFields>;
+
 export class ApmCpuUtilizationMetric extends ApmMetric {
+  // @ts-ignore
   constructor(opts) {
     super({
       ...opts,
@@ -57,6 +65,7 @@ export class ApmCpuUtilizationMetric extends ApmMetric {
     /*
      * Convert a counter of milliseconds of utilization time into a percentage of the bucket size
      */
+    // @ts-ignore
     this.calculation = ({ metric_deriv: metricDeriv } = {}, _key, _metric, bucketSizeInSeconds) => {
       if (metricDeriv) {
         const { value: metricDerivValue } = metricDeriv;
@@ -72,6 +81,7 @@ export class ApmCpuUtilizationMetric extends ApmMetric {
 }
 
 export class ApmEventsRateClusterMetric extends ApmClusterMetric {
+  // @ts-ignore
   constructor(opts) {
     super({
       ...opts,
@@ -83,6 +93,7 @@ export class ApmEventsRateClusterMetric extends ApmClusterMetric {
       }),
     });
 
+    // @ts-ignore
     this.aggs = {
       beats_uuids: {
         terms: {
@@ -92,6 +103,7 @@ export class ApmEventsRateClusterMetric extends ApmClusterMetric {
         aggs: {
           event_rate_per_beat: {
             max: {
+              // @ts-ignore
               field: this.field,
             },
           },
diff --git a/x-pack/plugins/monitoring/server/lib/metrics/beats/classes.js b/x-pack/plugins/monitoring/server/lib/metrics/beats/classes.ts
similarity index 91%
rename from x-pack/plugins/monitoring/server/lib/metrics/beats/classes.js
rename to x-pack/plugins/monitoring/server/lib/metrics/beats/classes.ts
index 4af71d2fd4bd..78e731cee888 100644
--- a/x-pack/plugins/monitoring/server/lib/metrics/beats/classes.js
+++ b/x-pack/plugins/monitoring/server/lib/metrics/beats/classes.ts
@@ -5,16 +5,20 @@
  * 2.0.
  */
 
+/* eslint-disable max-classes-per-file */
+
+import { i18n } from '@kbn/i18n';
+// @ts-ignore
 import { ClusterMetric, Metric } from '../classes';
 import { SMALL_FLOAT, LARGE_FLOAT, LARGE_BYTES } from '../../../../common/formatting';
 import { NORMALIZED_DERIVATIVE_UNIT } from '../../../../common/constants';
-import { i18n } from '@kbn/i18n';
 
 const perSecondUnitLabel = i18n.translate('xpack.monitoring.metrics.beats.perSecondUnitLabel', {
   defaultMessage: '/s',
 });
 
 export class BeatsClusterMetric extends ClusterMetric {
+  // @ts-ignore
   constructor(opts) {
     super({
       ...opts,
@@ -32,6 +36,7 @@ export class BeatsClusterMetric extends ClusterMetric {
 }
 
 export class BeatsEventsRateClusterMetric extends BeatsClusterMetric {
+  // @ts-ignore
   constructor(opts) {
     super({
       ...opts,
@@ -40,6 +45,7 @@ export class BeatsEventsRateClusterMetric extends BeatsClusterMetric {
       metricAgg: 'max',
       units: perSecondUnitLabel,
     });
+    // @ts-ignore
 
     this.aggs = {
       beats_uuids: {
@@ -50,6 +56,7 @@ export class BeatsEventsRateClusterMetric extends BeatsClusterMetric {
         aggs: {
           event_rate_per_beat: {
             max: {
+              // @ts-ignore
               field: this.field,
             },
           },
@@ -73,6 +80,7 @@ export class BeatsEventsRateClusterMetric extends BeatsClusterMetric {
 }
 
 export class BeatsMetric extends Metric {
+  // @ts-ignore
   constructor(opts) {
     super({
       ...opts,
@@ -89,7 +97,10 @@ export class BeatsMetric extends Metric {
   }
 }
 
+export type BeatsMetricFields = ReturnType<typeof BeatsMetric.getMetricFields>;
+
 export class BeatsByteRateClusterMetric extends BeatsEventsRateClusterMetric {
+  // @ts-ignore
   constructor(opts) {
     super({
       ...opts,
@@ -99,6 +110,7 @@ export class BeatsByteRateClusterMetric extends BeatsEventsRateClusterMetric {
 }
 
 export class BeatsEventsRateMetric extends BeatsMetric {
+  // @ts-ignore
   constructor(opts) {
     super({
       ...opts,
@@ -111,6 +123,7 @@ export class BeatsEventsRateMetric extends BeatsMetric {
 }
 
 export class BeatsByteRateMetric extends BeatsMetric {
+  // @ts-ignore
   constructor(opts) {
     super({
       ...opts,
@@ -123,6 +136,7 @@ export class BeatsByteRateMetric extends BeatsMetric {
 }
 
 export class BeatsCpuUtilizationMetric extends BeatsMetric {
+  // @ts-ignore
   constructor(opts) {
     super({
       ...opts,
@@ -135,6 +149,7 @@ export class BeatsCpuUtilizationMetric extends BeatsMetric {
     /*
      * Convert a counter of milliseconds of utilization time into a percentage of the bucket size
      */
+    // @ts-ignore
     this.calculation = ({ metric_deriv: metricDeriv } = {}, _key, _metric, bucketSizeInSeconds) => {
       if (metricDeriv) {
         const { value } = metricDeriv;
diff --git a/x-pack/plugins/monitoring/server/lib/metrics/index.js b/x-pack/plugins/monitoring/server/lib/metrics/index.ts
similarity index 69%
rename from x-pack/plugins/monitoring/server/lib/metrics/index.js
rename to x-pack/plugins/monitoring/server/lib/metrics/index.ts
index c2b24f653bc9..ba43a8c316d3 100644
--- a/x-pack/plugins/monitoring/server/lib/metrics/index.js
+++ b/x-pack/plugins/monitoring/server/lib/metrics/index.ts
@@ -5,9 +5,13 @@
  * 2.0.
  */
 
+// @ts-ignore
 export { ElasticsearchMetric } from './elasticsearch/classes';
+// @ts-ignore
 export { KibanaClusterMetric, KibanaMetric } from './kibana/classes';
-export { ApmMetric, ApmClusterMetric } from './apm/classes';
+export { ApmMetric, ApmClusterMetric, ApmMetricFields } from './apm/classes';
+// @ts-ignore
 export { LogstashClusterMetric, LogstashMetric } from './logstash/classes';
-export { BeatsClusterMetric, BeatsMetric } from './beats/classes';
+export { BeatsClusterMetric, BeatsMetric, BeatsMetricFields } from './beats/classes';
+// @ts-ignore
 export { metrics } from './metrics';
diff --git a/x-pack/plugins/monitoring/server/lib/normalize_version_string.js b/x-pack/plugins/monitoring/server/lib/normalize_version_string.ts
similarity index 90%
rename from x-pack/plugins/monitoring/server/lib/normalize_version_string.js
rename to x-pack/plugins/monitoring/server/lib/normalize_version_string.ts
index 359db54ae966..5d4930441484 100644
--- a/x-pack/plugins/monitoring/server/lib/normalize_version_string.js
+++ b/x-pack/plugins/monitoring/server/lib/normalize_version_string.ts
@@ -6,7 +6,7 @@
  */
 
 import { escape } from 'lodash';
-export function normalizeVersionString(string) {
+export function normalizeVersionString(string: string) {
   if (string) {
     // get just the number.number.number portion (filter out '-snapshot')
     const matches = string.match(/^\d+\.\d+.\d+/);
diff --git a/x-pack/plugins/monitoring/server/lib/standalone_clusters/index.js b/x-pack/plugins/monitoring/server/lib/standalone_clusters/index.ts
similarity index 92%
rename from x-pack/plugins/monitoring/server/lib/standalone_clusters/index.js
rename to x-pack/plugins/monitoring/server/lib/standalone_clusters/index.ts
index f15d3819fb03..edd18710b940 100644
--- a/x-pack/plugins/monitoring/server/lib/standalone_clusters/index.js
+++ b/x-pack/plugins/monitoring/server/lib/standalone_clusters/index.ts
@@ -5,6 +5,9 @@
  * 2.0.
  */
 
+// @ts-ignore
 export { hasStandaloneClusters } from './has_standalone_clusters';
+// @ts-ignore
 export { getStandaloneClusterDefinition } from './get_standalone_cluster_definition';
+// @ts-ignore
 export { standaloneClusterFilter } from './standalone_cluster_query_filter';
diff --git a/x-pack/plugins/monitoring/server/routes/api/v1/alerts/status.ts b/x-pack/plugins/monitoring/server/routes/api/v1/alerts/status.ts
index f77630e5d61a..27b21c342f03 100644
--- a/x-pack/plugins/monitoring/server/routes/api/v1/alerts/status.ts
+++ b/x-pack/plugins/monitoring/server/routes/api/v1/alerts/status.ts
@@ -41,7 +41,6 @@ export function alertStatusRoute(server: any, npRoute: RouteDependencies) {
 
         const status = await fetchStatus(
           rulesClient,
-          npRoute.licenseService,
           alertTypeIds,
           [clusterUuid],
           filters as CommonAlertFilter[]
diff --git a/x-pack/plugins/monitoring/server/routes/api/v1/cluster/cluster.js b/x-pack/plugins/monitoring/server/routes/api/v1/cluster/cluster.ts
similarity index 89%
rename from x-pack/plugins/monitoring/server/routes/api/v1/cluster/cluster.js
rename to x-pack/plugins/monitoring/server/routes/api/v1/cluster/cluster.ts
index e6de6ca984cb..2629d763d656 100644
--- a/x-pack/plugins/monitoring/server/routes/api/v1/cluster/cluster.js
+++ b/x-pack/plugins/monitoring/server/routes/api/v1/cluster/cluster.ts
@@ -7,10 +7,12 @@
 
 import { schema } from '@kbn/config-schema';
 import { getClustersFromRequest } from '../../../../lib/cluster/get_clusters_from_request';
+// @ts-ignore
 import { handleError } from '../../../../lib/errors';
 import { getIndexPatterns } from '../../../../lib/cluster/get_index_patterns';
+import { LegacyRequest, LegacyServer } from '../../../../types';
 
-export function clusterRoute(server) {
+export function clusterRoute(server: LegacyServer) {
   /*
    * Cluster Overview
    */
@@ -32,11 +34,11 @@ export function clusterRoute(server) {
         }),
       },
     },
-    handler: async (req) => {
+    handler: async (req: LegacyRequest) => {
       const config = server.config();
 
       const indexPatterns = getIndexPatterns(server, {
-        filebeatIndexPattern: config.get('monitoring.ui.logs.index'),
+        filebeatIndexPattern: config.get('monitoring.ui.logs.index')!,
       });
       const options = {
         clusterUuid: req.params.clusterUuid,
diff --git a/x-pack/plugins/monitoring/server/routes/api/v1/elasticsearch_settings/check/internal_monitoring.ts b/x-pack/plugins/monitoring/server/routes/api/v1/elasticsearch_settings/check/internal_monitoring.ts
index c2bad7b905c5..d05d60866d11 100644
--- a/x-pack/plugins/monitoring/server/routes/api/v1/elasticsearch_settings/check/internal_monitoring.ts
+++ b/x-pack/plugins/monitoring/server/routes/api/v1/elasticsearch_settings/check/internal_monitoring.ts
@@ -17,7 +17,7 @@ import {
 import { prefixIndexPattern } from '../../../../../lib/ccs_utils';
 // @ts-ignore
 import { handleError } from '../../../../../lib/errors';
-import { RouteDependencies } from '../../../../../types';
+import { RouteDependencies, LegacyServer } from '../../../../../types';
 
 const queryBody = {
   size: 0,
@@ -70,10 +70,7 @@ const checkLatestMonitoringIsLegacy = async (context: RequestHandlerContext, ind
   return counts;
 };
 
-export function internalMonitoringCheckRoute(
-  server: { config: () => unknown },
-  npRoute: RouteDependencies
-) {
+export function internalMonitoringCheckRoute(server: LegacyServer, npRoute: RouteDependencies) {
   npRoute.router.post(
     {
       path: '/api/monitoring/v1/elasticsearch_settings/check/internal_monitoring',
diff --git a/x-pack/plugins/monitoring/server/types.ts b/x-pack/plugins/monitoring/server/types.ts
index 07e56f0c0023..a057b72d89b2 100644
--- a/x-pack/plugins/monitoring/server/types.ts
+++ b/x-pack/plugins/monitoring/server/types.ts
@@ -30,6 +30,7 @@ import { LicensingPluginStart } from '../../licensing/server';
 import { PluginSetupContract as FeaturesPluginSetupContract } from '../../features/server';
 import { EncryptedSavedObjectsPluginSetup } from '../../encrypted_saved_objects/server';
 import { CloudSetup } from '../../cloud/server';
+import { ElasticsearchModifiedSource } from '../common/types/es';
 
 export interface MonitoringLicenseService {
   refresh: () => Promise<any>;
@@ -146,3 +147,20 @@ export interface LegacyServer {
     };
   };
 }
+
+export type Cluster = ElasticsearchModifiedSource & {
+  ml?: { jobs: any };
+  logs?: any;
+  alerts?: any;
+};
+
+export interface Bucket {
+  key: string;
+  uuids: {
+    buckets: unknown[];
+  };
+}
+
+export interface Aggregation {
+  buckets: Bucket[];
+}
diff --git a/x-pack/test/api_integration/apis/monitoring/standalone_cluster/fixtures/cluster.json b/x-pack/test/api_integration/apis/monitoring/standalone_cluster/fixtures/cluster.json
index 13535347f437..313481998d6c 100644
--- a/x-pack/test/api_integration/apis/monitoring/standalone_cluster/fixtures/cluster.json
+++ b/x-pack/test/api_integration/apis/monitoring/standalone_cluster/fixtures/cluster.json
@@ -1,61 +1,66 @@
-[{
-  "cluster_uuid": "__standalone_cluster__",
-  "license": {},
-  "elasticsearch": {
-    "cluster_stats": {
-      "indices": {
-        "docs": {},
-        "shards": {},
-        "store": {}
-      },
-      "nodes": {
-        "count": {
-          "total": {}
+[
+  {
+    "cluster_uuid": "__standalone_cluster__",
+    "license": {},
+    "elasticsearch": {
+      "cluster_stats": {
+        "indices": {
+          "docs": {},
+          "shards": {},
+          "store": {}
         },
-        "fs": {},
-        "jvm": {
-          "mem": {}
+        "nodes": {
+          "count": {
+            "total": {}
+          },
+          "fs": {},
+          "jvm": {
+            "mem": {}
+          }
         }
+      },
+      "logs": {
+        "enabled": false,
+        "reason": {
+          "clusterExists": false,
+          "indexPatternExists": false,
+          "indexPatternInTimeRangeExists": false,
+          "typeExistsAtAnyTime": false,
+          "usingStructuredLogs": false,
+          "nodeExists": null,
+          "indexExists": null,
+          "typeExists": false
+        },
+        "types": []
       }
     },
-    "logs": {
-      "enabled": false,
-      "reason": {
-        "clusterExists": false,
-        "indexPatternExists": false,
-        "indexPatternInTimeRangeExists": false,
-        "typeExistsAtAnyTime": false,
-        "usingStructuredLogs": false,
-        "nodeExists": null,
-        "indexExists": null,
-        "typeExists": false
-      },
-      "types": []
-    }
-  },
-  "logstash": {},
-  "kibana": {},
-  "beats": {
-    "totalEvents": 348,
-    "bytesSent": 319913,
+    "logstash": {},
+    "kibana": {},
     "beats": {
-      "total": 1,
-      "types": [{
-        "type": "Packetbeat",
-        "count": 1
-      }]
-    }
-  },
-  "apm": {
-    "totalEvents": 0,
-    "memRss": 0,
-    "apms": {
-      "total": 0
+      "totalEvents": 348,
+      "bytesSent": 319913,
+      "beats": {
+        "total": 1,
+        "types": [
+          {
+            "type": "Packetbeat",
+            "count": 1
+          }
+        ]
+      }
     },
-    "config": {
-      "container": false
+    "apm": {
+      "totalEvents": 0,
+      "memRss": 0,
+      "apms": {
+        "total": 0
+      },
+      "config": {
+        "container": false
+      },
+      "versions": []
     },
-    "versions": []
-  },
-  "isPrimary": false
-}]
+    "isPrimary": false,
+    "isCcrEnabled": false
+  }
+]