diff --git a/include/ircd/m/room/state.h b/include/ircd/m/room/state.h
index a8bc7dfec..aeacac149 100644
--- a/include/ircd/m/room/state.h
+++ b/include/ircd/m/room/state.h
@@ -39,8 +39,10 @@ struct ircd::m::room::state
 	const event::fetch::opts *fopts {nullptr};
 	mutable bool _not_present {false}; // cached result of !present()
 
+	// Check if this object is representing the present state or a past state.
 	bool present() const;
 
+	// Iterate the state
 	bool for_each(const types_bool &) const;
 	void for_each(const types &) const;
 	bool for_each(const string_view &type, const keys_bool &view) const;
@@ -77,10 +79,8 @@ struct ircd::m::room::state
 	void get(const string_view &type, const string_view &state_key, const event::closure_idx &) const;
 	void get(const string_view &type, const string_view &state_key, const event::id::closure &) const;
 	void get(const string_view &type, const string_view &state_key, const event::closure &) const;
-
-	// Fetch and return state event id
-	event::id::buf get(std::nothrow_t, const string_view &type, const string_view &state_key = "") const;
-	event::id::buf get(const string_view &type, const string_view &state_key = "") const;
+	event::idx get(std::nothrow_t, const string_view &type, const string_view &state_key = "") const;
+	event::idx get(const string_view &type, const string_view &state_key = "") const;
 
 	// Initiate a database prefetch on the state to cache for future access.
 	size_t prefetch(const string_view &type, const event::idx &start = 0, const event::idx &stop = 0) const;
diff --git a/ircd/m_room.cc b/ircd/m_room.cc
index c0aef91ac..dbd8a35e6 100644
--- a/ircd/m_room.cc
+++ b/ircd/m_room.cc
@@ -893,32 +893,32 @@ ircd::m::room::state::state(const m::room &room,
 {
 }
 
-ircd::m::event::id::buf
+ircd::m::event::idx
 ircd::m::room::state::get(const string_view &type,
                           const string_view &state_key)
 const
 {
-	event::id::buf ret;
-	get(type, state_key, event::id::closure{[&ret]
-	(const event::id &event_id)
+	event::idx ret;
+	get(type, state_key, event::closure_idx{[&ret]
+	(const event::idx &event_idx)
 	{
-		ret = event_id;
+		ret = event_idx;
 	}});
 
 	return ret;
 }
 
-ircd::m::event::id::buf
+ircd::m::event::idx
 ircd::m::room::state::get(std::nothrow_t,
                           const string_view &type,
                           const string_view &state_key)
 const
 {
-	event::id::buf ret;
-	get(std::nothrow, type, state_key, event::id::closure{[&ret]
-	(const event::id &event_id)
+	event::idx ret{0};
+	get(std::nothrow, type, state_key, event::closure_idx{[&ret]
+	(const event::idx &event_idx)
 	{
-		ret = event_id;
+		ret = event_idx;
 	}});
 
 	return ret;
diff --git a/modules/federation/make_join.cc b/modules/federation/make_join.cc
index ce3cea541..7aefc6857 100644
--- a/modules/federation/make_join.cc
+++ b/modules/federation/make_join.cc
@@ -86,17 +86,22 @@ get__make_join(client &client,
 		room_id
 	};
 
-	auto auth_event_id
+	auto auth_event_idx
 	{
 		state.get(std::nothrow, "m.room.member", user_id)
 	};
 
-	if(!auth_event_id)
-		auth_event_id = state.get("m.room.create");
+	if(!auth_event_idx)
+		auth_event_idx = state.get("m.room.create");
+
+	const auto auth_event_id
+	{
+		m::event_id(auth_event_idx)
+	};
 
 	const m::event::fetch aevf
 	{
-		auth_event_id, std::nothrow
+		auth_event_idx, std::nothrow
 	};
 
 	const json::value auth[]
diff --git a/modules/m_room.cc b/modules/m_room.cc
index 83d535b22..ade7bff3a 100644
--- a/modules/m_room.cc
+++ b/modules/m_room.cc
@@ -319,14 +319,14 @@ is_complete(const m::room &room)
 		room
 	};
 
-	const auto create_id
+	const auto create_idx
 	{
 		state.get("m.room.create")
 	};
 
 	room::messages it
 	{
-		room, create_id, &fopts
+		room, create_idx, &fopts
 	};
 
 	int64_t depth(-1);
@@ -386,7 +386,7 @@ state__rebuild_present(const m::room &room)
 		room
 	};
 
-	const auto create_id
+	const auto create_idx
 	{
 		state.get("m.room.create")
 	};
@@ -398,7 +398,7 @@ state__rebuild_present(const m::room &room)
 
 	m::room::messages it
 	{
-		room, create_id, &fopts
+		room, create_idx, &fopts
 	};
 
 	if(!it)
@@ -440,7 +440,7 @@ state__rebuild_history(const m::room &room)
 		room
 	};
 
-	const auto create_id
+	const auto create_idx
 	{
 		state.get("m.room.create")
 	};
@@ -452,7 +452,7 @@ state__rebuild_history(const m::room &room)
 
 	m::room::messages it
 	{
-		room, create_id, &fopts
+		room, create_idx, &fopts
 	};
 
 	if(!it)
@@ -607,7 +607,7 @@ head__rebuild(const m::room &room)
 {
 	size_t ret{0};
 	const m::room::state state{room};
-	const auto create_id
+	const auto create_idx
 	{
 		state.get("m.room.create")
 	};
@@ -619,7 +619,7 @@ head__rebuild(const m::room &room)
 
 	m::room::messages it
 	{
-		room, create_id, &fopts
+		room, create_idx, &fopts
 	};
 
 	if(!it)