diff --git a/appservice/consumers/roomserver.go b/appservice/consumers/roomserver.go
index bb4df790..1657fe54 100644
--- a/appservice/consumers/roomserver.go
+++ b/appservice/consumers/roomserver.go
@@ -91,60 +91,13 @@ func (s *OutputRoomEventConsumer) onMessage(msg *sarama.ConsumerMessage) error {
 		return nil
 	}
 
-	ev := output.NewRoomEvent.Event
-	log.WithFields(log.Fields{
-		"event_id": ev.EventID(),
-		"room_id":  ev.RoomID(),
-		"type":     ev.Type(),
-	}).Info("appservice received an event from roomserver")
-
-	missingEvents, err := s.lookupMissingStateEvents(output.NewRoomEvent.AddsStateEventIDs, ev)
-	if err != nil {
-		return err
-	}
-	events := append(missingEvents, ev)
+	events := []gomatrixserverlib.HeaderedEvent{output.NewRoomEvent.Event}
+	events = append(events, output.NewRoomEvent.AddStateEvents...)
 
 	// Send event to any relevant application services
 	return s.filterRoomserverEvents(context.TODO(), events)
 }
 
-// lookupMissingStateEvents looks up the state events that are added by a new event,
-// and returns any not already present.
-func (s *OutputRoomEventConsumer) lookupMissingStateEvents(
-	addsStateEventIDs []string, event gomatrixserverlib.HeaderedEvent,
-) ([]gomatrixserverlib.HeaderedEvent, error) {
-	// Fast path if there aren't any new state events.
-	if len(addsStateEventIDs) == 0 {
-		return []gomatrixserverlib.HeaderedEvent{}, nil
-	}
-
-	// Fast path if the only state event added is the event itself.
-	if len(addsStateEventIDs) == 1 && addsStateEventIDs[0] == event.EventID() {
-		return []gomatrixserverlib.HeaderedEvent{}, nil
-	}
-
-	result := []gomatrixserverlib.HeaderedEvent{}
-	missing := []string{}
-	for _, id := range addsStateEventIDs {
-		if id != event.EventID() {
-			// If the event isn't the current one, add it to the list of events
-			// to retrieve from the roomserver
-			missing = append(missing, id)
-		}
-	}
-
-	// Request the missing events from the roomserver
-	eventReq := api.QueryEventsByIDRequest{EventIDs: missing}
-	var eventResp api.QueryEventsByIDResponse
-	if err := s.rsAPI.QueryEventsByID(context.TODO(), &eventReq, &eventResp); err != nil {
-		return nil, err
-	}
-
-	result = append(result, eventResp.Events...)
-
-	return result, nil
-}
-
 // filterRoomserverEvents takes in events and decides whether any of them need
 // to be passed on to an external application service. It does this by checking
 // each namespace of each registered application service, and if there is a
diff --git a/clientapi/consumers/roomserver.go b/clientapi/consumers/roomserver.go
index bd8ac1dc..caa028ba 100644
--- a/clientapi/consumers/roomserver.go
+++ b/clientapi/consumers/roomserver.go
@@ -84,63 +84,9 @@ func (s *OutputRoomEventConsumer) onMessage(msg *sarama.ConsumerMessage) error {
 		return nil
 	}
 
-	ev := output.NewRoomEvent.Event
-	log.WithFields(log.Fields{
-		"event_id": ev.EventID(),
-		"room_id":  ev.RoomID(),
-		"type":     ev.Type(),
-	}).Info("received event from roomserver")
-
-	events, err := s.lookupStateEvents(output.NewRoomEvent.AddsStateEventIDs, ev.Event)
-	if err != nil {
-		return err
-	}
-
-	return s.db.UpdateMemberships(context.TODO(), events, output.NewRoomEvent.RemovesStateEventIDs)
-}
-
-// lookupStateEvents looks up the state events that are added by a new event.
-func (s *OutputRoomEventConsumer) lookupStateEvents(
-	addsStateEventIDs []string, event gomatrixserverlib.Event,
-) ([]gomatrixserverlib.Event, error) {
-	// Fast path if there aren't any new state events.
-	if len(addsStateEventIDs) == 0 {
-		// If the event is a membership update (e.g. for a profile update), it won't
-		// show up in AddsStateEventIDs, so we need to add it manually
-		if event.Type() == "m.room.member" {
-			return []gomatrixserverlib.Event{event}, nil
-		}
-		return nil, nil
-	}
-
-	// Fast path if the only state event added is the event itself.
-	if len(addsStateEventIDs) == 1 && addsStateEventIDs[0] == event.EventID() {
-		return []gomatrixserverlib.Event{event}, nil
-	}
-
-	result := []gomatrixserverlib.Event{}
-	missing := []string{}
-	for _, id := range addsStateEventIDs {
-		// Append the current event in the results if its ID is in the events list
-		if id == event.EventID() {
-			result = append(result, event)
-		} else {
-			// If the event isn't the current one, add it to the list of events
-			// to retrieve from the roomserver
-			missing = append(missing, id)
-		}
-	}
-
-	// Request the missing events from the roomserver
-	eventReq := api.QueryEventsByIDRequest{EventIDs: missing}
-	var eventResp api.QueryEventsByIDResponse
-	if err := s.rsAPI.QueryEventsByID(context.TODO(), &eventReq, &eventResp); err != nil {
-		return nil, err
-	}
-
-	for _, headeredEvent := range eventResp.Events {
-		result = append(result, headeredEvent.Event)
-	}
-
-	return result, nil
+	return s.db.UpdateMemberships(
+		context.TODO(),
+		gomatrixserverlib.UnwrapEventHeaders(output.NewRoomEvent.AddsState()),
+		output.NewRoomEvent.RemovesStateEventIDs,
+	)
 }
diff --git a/federationapi/routing/backfill.go b/federationapi/routing/backfill.go
index 10bc6263..f906c73c 100644
--- a/federationapi/routing/backfill.go
+++ b/federationapi/routing/backfill.go
@@ -37,7 +37,7 @@ func Backfill(
 	roomID string,
 	cfg *config.Dendrite,
 ) util.JSONResponse {
-	var res api.QueryBackfillResponse
+	var res api.PerformBackfillResponse
 	var eIDs []string
 	var limit string
 	var exists bool
@@ -68,7 +68,7 @@ func Backfill(
 	}
 
 	// Populate the request.
-	req := api.QueryBackfillRequest{
+	req := api.PerformBackfillRequest{
 		RoomID: roomID,
 		// we don't know who the successors are for these events, which won't
 		// be a problem because we don't use that information when servicing /backfill requests,
@@ -87,8 +87,8 @@ func Backfill(
 	}
 
 	// Query the roomserver.
-	if err = rsAPI.QueryBackfill(httpReq.Context(), &req, &res); err != nil {
-		util.GetLogger(httpReq.Context()).WithError(err).Error("query.QueryBackfill failed")
+	if err = rsAPI.PerformBackfill(httpReq.Context(), &req, &res); err != nil {
+		util.GetLogger(httpReq.Context()).WithError(err).Error("query.PerformBackfill failed")
 		return jsonerror.InternalServerError()
 	}
 
diff --git a/federationapi/routing/send_test.go b/federationapi/routing/send_test.go
index 9081a870..adae7c22 100644
--- a/federationapi/routing/send_test.go
+++ b/federationapi/routing/send_test.go
@@ -211,10 +211,10 @@ func (t *testRoomserverAPI) QueryStateAndAuthChain(
 }
 
 // Query a given amount (or less) of events prior to a given set of events.
-func (t *testRoomserverAPI) QueryBackfill(
+func (t *testRoomserverAPI) PerformBackfill(
 	ctx context.Context,
-	request *api.QueryBackfillRequest,
-	response *api.QueryBackfillResponse,
+	request *api.PerformBackfillRequest,
+	response *api.PerformBackfillResponse,
 ) error {
 	return fmt.Errorf("not implemented")
 }
diff --git a/federationsender/consumers/roomserver.go b/federationsender/consumers/roomserver.go
index 5f8a555b..a15937f9 100644
--- a/federationsender/consumers/roomserver.go
+++ b/federationsender/consumers/roomserver.go
@@ -131,11 +131,7 @@ func (s *OutputRoomEventConsumer) onMessage(msg *sarama.ConsumerMessage) error {
 // processMessage updates the list of currently joined hosts in the room
 // and then sends the event to the hosts that were joined before the event.
 func (s *OutputRoomEventConsumer) processMessage(ore api.OutputNewRoomEvent) error {
-	addsStateEvents, err := s.lookupStateEvents(ore.AddsStateEventIDs, ore.Event.Event)
-	if err != nil {
-		return err
-	}
-	addsJoinedHosts, err := joinedHostsFromEvents(addsStateEvents)
+	addsJoinedHosts, err := joinedHostsFromEvents(gomatrixserverlib.UnwrapEventHeaders(ore.AddsState()))
 	if err != nil {
 		return err
 	}
diff --git a/publicroomsapi/consumers/roomserver.go b/publicroomsapi/consumers/roomserver.go
index c513d3b2..ba187cb1 100644
--- a/publicroomsapi/consumers/roomserver.go
+++ b/publicroomsapi/consumers/roomserver.go
@@ -78,20 +78,6 @@ func (s *OutputRoomEventConsumer) onMessage(msg *sarama.ConsumerMessage) error {
 		return nil
 	}
 
-	ev := output.NewRoomEvent.Event
-	log.WithFields(log.Fields{
-		"event_id": ev.EventID(),
-		"room_id":  ev.RoomID(),
-		"type":     ev.Type(),
-	}).Info("received event from roomserver")
-
-	addQueryReq := api.QueryEventsByIDRequest{EventIDs: output.NewRoomEvent.AddsStateEventIDs}
-	var addQueryRes api.QueryEventsByIDResponse
-	if err := s.rsAPI.QueryEventsByID(context.TODO(), &addQueryReq, &addQueryRes); err != nil {
-		log.Warn(err)
-		return err
-	}
-
 	remQueryReq := api.QueryEventsByIDRequest{EventIDs: output.NewRoomEvent.RemovesStateEventIDs}
 	var remQueryRes api.QueryEventsByIDResponse
 	if err := s.rsAPI.QueryEventsByID(context.TODO(), &remQueryReq, &remQueryRes); err != nil {
@@ -100,9 +86,10 @@ func (s *OutputRoomEventConsumer) onMessage(msg *sarama.ConsumerMessage) error {
 	}
 
 	var addQueryEvents, remQueryEvents []gomatrixserverlib.Event
-	for _, headeredEvent := range addQueryRes.Events {
+	for _, headeredEvent := range output.NewRoomEvent.AddsState() {
 		addQueryEvents = append(addQueryEvents, headeredEvent.Event)
 	}
+	addQueryEvents = append(addQueryEvents, output.NewRoomEvent.Event.Unwrap())
 	for _, headeredEvent := range remQueryRes.Events {
 		remQueryEvents = append(remQueryEvents, headeredEvent.Event)
 	}
diff --git a/roomserver/api/api.go b/roomserver/api/api.go
index 3a2ad059..967f58ba 100644
--- a/roomserver/api/api.go
+++ b/roomserver/api/api.go
@@ -89,10 +89,10 @@ type RoomserverInternalAPI interface {
 	) error
 
 	// Query a given amount (or less) of events prior to a given set of events.
-	QueryBackfill(
+	PerformBackfill(
 		ctx context.Context,
-		request *QueryBackfillRequest,
-		response *QueryBackfillResponse,
+		request *PerformBackfillRequest,
+		response *PerformBackfillResponse,
 	) error
 
 	// Asks for the default room version as preferred by the server.
diff --git a/roomserver/api/output.go b/roomserver/api/output.go
index 92a468a9..2bbd97af 100644
--- a/roomserver/api/output.go
+++ b/roomserver/api/output.go
@@ -63,6 +63,13 @@ type OutputNewRoomEvent struct {
 	// Together with RemovesStateEventIDs this allows the receiver to keep an up to date
 	// view of the current state of the room.
 	AddsStateEventIDs []string `json:"adds_state_event_ids"`
+	// All extra newly added state events. This is only set if there are *extra* events
+	// other than `Event`. This can happen when forks get merged because state resolution
+	// may decide a bunch of state events on one branch are now valid, so they will be
+	// present in this list. This is useful when trying to maintain the current state of a room
+	// as to do so you need to include both these events and `Event`.
+	AddStateEvents []gomatrixserverlib.HeaderedEvent `json:"adds_state_events"`
+
 	// The state event IDs that were removed from the state of the room by this event.
 	RemovesStateEventIDs []string `json:"removes_state_event_ids"`
 	// The ID of the event that was output before this event.
@@ -112,6 +119,26 @@ type OutputNewRoomEvent struct {
 	TransactionID *TransactionID `json:"transaction_id"`
 }
 
+// AddsState returns all added state events from this event.
+//
+// This function is needed because `AddStateEvents` will not include a copy of
+// the original event to save space, so you cannot use that slice alone.
+// Instead, use this function which will add the original event if it is present
+// in `AddsStateEventIDs`.
+func (ore *OutputNewRoomEvent) AddsState() []gomatrixserverlib.HeaderedEvent {
+	includeOutputEvent := false
+	for _, id := range ore.AddsStateEventIDs {
+		if id == ore.Event.EventID() {
+			includeOutputEvent = true
+			break
+		}
+	}
+	if !includeOutputEvent {
+		return ore.AddStateEvents
+	}
+	return append(ore.AddStateEvents, ore.Event)
+}
+
 // An OutputNewInviteEvent is written whenever an invite becomes active.
 // Invite events can be received outside of an existing room so have to be
 // tracked separately from the room events themselves.
diff --git a/roomserver/api/perform.go b/roomserver/api/perform.go
index 1cf54144..3e5cae1b 100644
--- a/roomserver/api/perform.go
+++ b/roomserver/api/perform.go
@@ -2,6 +2,7 @@ package api
 
 import (
 	"github.com/matrix-org/gomatrixserverlib"
+	"github.com/matrix-org/util"
 )
 
 type PerformJoinRequest struct {
@@ -22,3 +23,31 @@ type PerformLeaveRequest struct {
 
 type PerformLeaveResponse struct {
 }
+
+// PerformBackfillRequest is a request to PerformBackfill.
+type PerformBackfillRequest struct {
+	// The room to backfill
+	RoomID string `json:"room_id"`
+	// A map of backwards extremity event ID to a list of its prev_event IDs.
+	BackwardsExtremities map[string][]string `json:"backwards_extremities"`
+	// The maximum number of events to retrieve.
+	Limit int `json:"limit"`
+	// The server interested in the events.
+	ServerName gomatrixserverlib.ServerName `json:"server_name"`
+}
+
+// PrevEventIDs returns the prev_event IDs of all backwards extremities, de-duplicated in a lexicographically sorted order.
+func (r *PerformBackfillRequest) PrevEventIDs() []string {
+	var prevEventIDs []string
+	for _, pes := range r.BackwardsExtremities {
+		prevEventIDs = append(prevEventIDs, pes...)
+	}
+	prevEventIDs = util.UniqueStrings(prevEventIDs)
+	return prevEventIDs
+}
+
+// PerformBackfillResponse is a response to PerformBackfill.
+type PerformBackfillResponse struct {
+	// Missing events, arbritrary order.
+	Events []gomatrixserverlib.HeaderedEvent `json:"events"`
+}
diff --git a/roomserver/api/query.go b/roomserver/api/query.go
index c9a46ae9..b1525342 100644
--- a/roomserver/api/query.go
+++ b/roomserver/api/query.go
@@ -18,7 +18,6 @@ package api
 
 import (
 	"github.com/matrix-org/gomatrixserverlib"
-	"github.com/matrix-org/util"
 )
 
 // QueryLatestEventsAndStateRequest is a request to QueryLatestEventsAndState
@@ -204,34 +203,6 @@ type QueryStateAndAuthChainResponse struct {
 	AuthChainEvents []gomatrixserverlib.HeaderedEvent `json:"auth_chain_events"`
 }
 
-// QueryBackfillRequest is a request to QueryBackfill.
-type QueryBackfillRequest struct {
-	// The room to backfill
-	RoomID string `json:"room_id"`
-	// A map of backwards extremity event ID to a list of its prev_event IDs.
-	BackwardsExtremities map[string][]string `json:"backwards_extremities"`
-	// The maximum number of events to retrieve.
-	Limit int `json:"limit"`
-	// The server interested in the events.
-	ServerName gomatrixserverlib.ServerName `json:"server_name"`
-}
-
-// PrevEventIDs returns the prev_event IDs of all backwards extremities, de-duplicated in a lexicographically sorted order.
-func (r *QueryBackfillRequest) PrevEventIDs() []string {
-	var prevEventIDs []string
-	for _, pes := range r.BackwardsExtremities {
-		prevEventIDs = append(prevEventIDs, pes...)
-	}
-	prevEventIDs = util.UniqueStrings(prevEventIDs)
-	return prevEventIDs
-}
-
-// QueryBackfillResponse is a response to QueryBackfill.
-type QueryBackfillResponse struct {
-	// Missing events, arbritrary order.
-	Events []gomatrixserverlib.HeaderedEvent `json:"events"`
-}
-
 // QueryRoomVersionCapabilitiesRequest asks for the default room version
 type QueryRoomVersionCapabilitiesRequest struct{}
 
diff --git a/roomserver/internal/input_latest_events.go b/roomserver/internal/input_latest_events.go
index aea85ca9..e69307ad 100644
--- a/roomserver/internal/input_latest_events.go
+++ b/roomserver/internal/input_latest_events.go
@@ -19,6 +19,7 @@ package internal
 import (
 	"bytes"
 	"context"
+	"fmt"
 
 	"github.com/matrix-org/dendrite/internal"
 	"github.com/matrix-org/dendrite/roomserver/api"
@@ -310,24 +311,11 @@ func (u *latestEventsUpdater) makeOutputNewRoomEvent() (*api.OutputEvent, error)
 		TransactionID:   u.transactionID,
 	}
 
-	var stateEventNIDs []types.EventNID
-	for _, entry := range u.added {
-		stateEventNIDs = append(stateEventNIDs, entry.EventNID)
-	}
-	for _, entry := range u.removed {
-		stateEventNIDs = append(stateEventNIDs, entry.EventNID)
-	}
-	for _, entry := range u.stateBeforeEventRemoves {
-		stateEventNIDs = append(stateEventNIDs, entry.EventNID)
-	}
-	for _, entry := range u.stateBeforeEventAdds {
-		stateEventNIDs = append(stateEventNIDs, entry.EventNID)
-	}
-	stateEventNIDs = stateEventNIDs[:util.SortAndUnique(eventNIDSorter(stateEventNIDs))]
-	eventIDMap, err := u.api.DB.EventIDs(u.ctx, stateEventNIDs)
+	eventIDMap, err := u.stateEventMap()
 	if err != nil {
 		return nil, err
 	}
+
 	for _, entry := range u.added {
 		ore.AddsStateEventIDs = append(ore.AddsStateEventIDs, eventIDMap[entry.EventNID])
 	}
@@ -342,12 +330,60 @@ func (u *latestEventsUpdater) makeOutputNewRoomEvent() (*api.OutputEvent, error)
 	}
 	ore.SendAsServer = u.sendAsServer
 
+	// include extra state events if they were added as nearly every downstream component will care about it
+	// and we'd rather not have them all hit QueryEventsByID at the same time!
+	if len(ore.AddsStateEventIDs) > 0 {
+		ore.AddStateEvents, err = u.extraEventsForIDs(roomVersion, ore.AddsStateEventIDs)
+		if err != nil {
+			return nil, fmt.Errorf("failed to load add_state_events from db: %w", err)
+		}
+	}
+
 	return &api.OutputEvent{
 		Type:         api.OutputTypeNewRoomEvent,
 		NewRoomEvent: &ore,
 	}, nil
 }
 
+// extraEventsForIDs returns the full events for the event IDs given, but does not include the current event being
+// updated.
+func (u *latestEventsUpdater) extraEventsForIDs(roomVersion gomatrixserverlib.RoomVersion, eventIDs []string) ([]gomatrixserverlib.HeaderedEvent, error) {
+	var extraEventIDs []string
+	for _, e := range eventIDs {
+		if e == u.event.EventID() {
+			continue
+		}
+		extraEventIDs = append(extraEventIDs, e)
+	}
+	if len(extraEventIDs) == 0 {
+		return nil, nil
+	}
+	extraEvents, err := u.api.DB.EventsFromIDs(u.ctx, extraEventIDs)
+	if err != nil {
+		return nil, err
+	}
+	var h []gomatrixserverlib.HeaderedEvent
+	for _, e := range extraEvents {
+		h = append(h, e.Headered(roomVersion))
+	}
+	return h, nil
+}
+
+// retrieve an event nid -> event ID map for all events that need updating
+func (u *latestEventsUpdater) stateEventMap() (map[types.EventNID]string, error) {
+	var stateEventNIDs []types.EventNID
+	var allStateEntries []types.StateEntry
+	allStateEntries = append(allStateEntries, u.added...)
+	allStateEntries = append(allStateEntries, u.removed...)
+	allStateEntries = append(allStateEntries, u.stateBeforeEventRemoves...)
+	allStateEntries = append(allStateEntries, u.stateBeforeEventAdds...)
+	for _, entry := range allStateEntries {
+		stateEventNIDs = append(stateEventNIDs, entry.EventNID)
+	}
+	stateEventNIDs = stateEventNIDs[:util.SortAndUnique(eventNIDSorter(stateEventNIDs))]
+	return u.api.DB.EventIDs(u.ctx, stateEventNIDs)
+}
+
 type eventNIDSorter []types.EventNID
 
 func (s eventNIDSorter) Len() int           { return len(s) }
diff --git a/roomserver/internal/query_backfill.go b/roomserver/internal/perform_backfill.go
similarity index 100%
rename from roomserver/internal/query_backfill.go
rename to roomserver/internal/perform_backfill.go
diff --git a/roomserver/internal/query.go b/roomserver/internal/query.go
index aea93388..375ddc23 100644
--- a/roomserver/internal/query.go
+++ b/roomserver/internal/query.go
@@ -441,11 +441,11 @@ func (r *RoomserverInternalAPI) QueryMissingEvents(
 	return err
 }
 
-// QueryBackfill implements api.RoomServerQueryAPI
-func (r *RoomserverInternalAPI) QueryBackfill(
+// PerformBackfill implements api.RoomServerQueryAPI
+func (r *RoomserverInternalAPI) PerformBackfill(
 	ctx context.Context,
-	request *api.QueryBackfillRequest,
-	response *api.QueryBackfillResponse,
+	request *api.PerformBackfillRequest,
+	response *api.PerformBackfillResponse,
 ) error {
 	// if we are requesting the backfill then we need to do a federation hit
 	// TODO: we could be more sensible and fetch as many events we already have then request the rest
@@ -489,7 +489,7 @@ func (r *RoomserverInternalAPI) QueryBackfill(
 	return err
 }
 
-func (r *RoomserverInternalAPI) backfillViaFederation(ctx context.Context, req *api.QueryBackfillRequest, res *api.QueryBackfillResponse) error {
+func (r *RoomserverInternalAPI) backfillViaFederation(ctx context.Context, req *api.PerformBackfillRequest, res *api.PerformBackfillResponse) error {
 	roomVer, err := r.DB.GetRoomVersionForRoom(ctx, req.RoomID)
 	if err != nil {
 		return fmt.Errorf("backfillViaFederation: unknown room version for room %s : %w", req.RoomID, err)
@@ -647,7 +647,7 @@ func (r *RoomserverInternalAPI) scanEventTree(
 	var pre string
 
 	// TODO: add tests for this function to ensure it meets the contract that callers expect (and doc what that is supposed to be)
-	// Currently, callers like QueryBackfill will call scanEventTree with a pre-populated `visited` map, assuming that by doing
+	// Currently, callers like PerformBackfill will call scanEventTree with a pre-populated `visited` map, assuming that by doing
 	// so means that the events in that map will NOT be returned from this function. That is not currently true, resulting in
 	// duplicate events being sent in response to /backfill requests.
 	initialIgnoreList := make(map[string]bool, len(visited))
diff --git a/roomserver/inthttp/client.go b/roomserver/inthttp/client.go
index 6f5e882e..1244300d 100644
--- a/roomserver/inthttp/client.go
+++ b/roomserver/inthttp/client.go
@@ -24,8 +24,9 @@ const (
 	RoomserverInputRoomEventsPath = "/roomserver/inputRoomEvents"
 
 	// Perform operations
-	RoomserverPerformJoinPath  = "/roomserver/performJoin"
-	RoomserverPerformLeavePath = "/roomserver/performLeave"
+	RoomserverPerformJoinPath     = "/roomserver/performJoin"
+	RoomserverPerformLeavePath    = "/roomserver/performLeave"
+	RoomserverPerformBackfillPath = "/roomserver/performBackfill"
 
 	// Query operations
 	RoomserverQueryLatestEventsAndStatePath    = "/roomserver/queryLatestEventsAndState"
@@ -36,7 +37,6 @@ const (
 	RoomserverQueryServerAllowedToSeeEventPath = "/roomserver/queryServerAllowedToSeeEvent"
 	RoomserverQueryMissingEventsPath           = "/roomserver/queryMissingEvents"
 	RoomserverQueryStateAndAuthChainPath       = "/roomserver/queryStateAndAuthChain"
-	RoomserverQueryBackfillPath                = "/roomserver/queryBackfill"
 	RoomserverQueryRoomVersionCapabilitiesPath = "/roomserver/queryRoomVersionCapabilities"
 	RoomserverQueryRoomVersionForRoomPath      = "/roomserver/queryRoomVersionForRoom"
 )
@@ -274,16 +274,16 @@ func (h *httpRoomserverInternalAPI) QueryStateAndAuthChain(
 	return internalHTTP.PostJSON(ctx, span, h.httpClient, apiURL, request, response)
 }
 
-// QueryBackfill implements RoomServerQueryAPI
-func (h *httpRoomserverInternalAPI) QueryBackfill(
+// PerformBackfill implements RoomServerQueryAPI
+func (h *httpRoomserverInternalAPI) PerformBackfill(
 	ctx context.Context,
-	request *api.QueryBackfillRequest,
-	response *api.QueryBackfillResponse,
+	request *api.PerformBackfillRequest,
+	response *api.PerformBackfillResponse,
 ) error {
-	span, ctx := opentracing.StartSpanFromContext(ctx, "QueryBackfill")
+	span, ctx := opentracing.StartSpanFromContext(ctx, "PerformBackfill")
 	defer span.Finish()
 
-	apiURL := h.roomserverURL + RoomserverQueryBackfillPath
+	apiURL := h.roomserverURL + RoomserverPerformBackfillPath
 	return internalHTTP.PostJSON(ctx, span, h.httpClient, apiURL, request, response)
 }
 
diff --git a/roomserver/inthttp/server.go b/roomserver/inthttp/server.go
index 3a13ce37..8ac815f3 100644
--- a/roomserver/inthttp/server.go
+++ b/roomserver/inthttp/server.go
@@ -165,14 +165,14 @@ func AddRoutes(r api.RoomserverInternalAPI, internalAPIMux *mux.Router) {
 		}),
 	)
 	internalAPIMux.Handle(
-		RoomserverQueryBackfillPath,
-		internal.MakeInternalAPI("QueryBackfill", func(req *http.Request) util.JSONResponse {
-			var request api.QueryBackfillRequest
-			var response api.QueryBackfillResponse
+		RoomserverPerformBackfillPath,
+		internal.MakeInternalAPI("PerformBackfill", func(req *http.Request) util.JSONResponse {
+			var request api.PerformBackfillRequest
+			var response api.PerformBackfillResponse
 			if err := json.NewDecoder(req.Body).Decode(&request); err != nil {
 				return util.ErrorResponse(err)
 			}
-			if err := r.QueryBackfill(req.Context(), &request, &response); err != nil {
+			if err := r.PerformBackfill(req.Context(), &request, &response); err != nil {
 				return util.ErrorResponse(err)
 			}
 			return util.JSONResponse{Code: http.StatusOK, JSON: &response}
diff --git a/syncapi/consumers/roomserver.go b/syncapi/consumers/roomserver.go
index 055f7660..13597682 100644
--- a/syncapi/consumers/roomserver.go
+++ b/syncapi/consumers/roomserver.go
@@ -17,7 +17,6 @@ package consumers
 import (
 	"context"
 	"encoding/json"
-	"fmt"
 
 	"github.com/Shopify/sarama"
 	"github.com/matrix-org/dendrite/internal"
@@ -105,17 +104,9 @@ func (s *OutputRoomEventConsumer) onNewRoomEvent(
 		"room_version": ev.RoomVersion,
 	}).Info("received event from roomserver")
 
-	addsStateEvents, err := s.lookupStateEvents(msg.AddsStateEventIDs, ev)
-	if err != nil {
-		log.WithFields(log.Fields{
-			"event":      string(ev.JSON()),
-			log.ErrorKey: err,
-			"add":        msg.AddsStateEventIDs,
-			"del":        msg.RemovesStateEventIDs,
-		}).Panicf("roomserver output log: state event lookup failure")
-	}
+	addsStateEvents := msg.AddsState()
 
-	ev, err = s.updateStateEvent(ev)
+	ev, err := s.updateStateEvent(ev)
 	if err != nil {
 		return err
 	}
@@ -185,63 +176,6 @@ func (s *OutputRoomEventConsumer) onRetireInviteEvent(
 	return nil
 }
 
-// lookupStateEvents looks up the state events that are added by a new event.
-func (s *OutputRoomEventConsumer) lookupStateEvents(
-	addsStateEventIDs []string, event gomatrixserverlib.HeaderedEvent,
-) ([]gomatrixserverlib.HeaderedEvent, error) {
-	// Fast path if there aren't any new state events.
-	if len(addsStateEventIDs) == 0 {
-		return nil, nil
-	}
-
-	// Fast path if the only state event added is the event itself.
-	if len(addsStateEventIDs) == 1 && addsStateEventIDs[0] == event.EventID() {
-		return []gomatrixserverlib.HeaderedEvent{event}, nil
-	}
-
-	// Check if this is re-adding a state events that we previously processed
-	// If we have previously received a state event it may still be in
-	// our event database.
-	result, err := s.db.Events(context.TODO(), addsStateEventIDs)
-	if err != nil {
-		return nil, err
-	}
-	missing := missingEventsFrom(result, addsStateEventIDs)
-
-	// Check if event itself is being added.
-	for _, eventID := range missing {
-		if eventID == event.EventID() {
-			result = append(result, event)
-			break
-		}
-	}
-	missing = missingEventsFrom(result, addsStateEventIDs)
-
-	if len(missing) == 0 {
-		return result, nil
-	}
-
-	// At this point the missing events are neither the event itself nor are
-	// they present in our local database. Our only option is to fetch them
-	// from the roomserver using the query API.
-	eventReq := api.QueryEventsByIDRequest{EventIDs: missing}
-	var eventResp api.QueryEventsByIDResponse
-	if err := s.rsAPI.QueryEventsByID(context.TODO(), &eventReq, &eventResp); err != nil {
-		return nil, err
-	}
-
-	result = append(result, eventResp.Events...)
-	missing = missingEventsFrom(result, addsStateEventIDs)
-
-	if len(missing) != 0 {
-		return nil, fmt.Errorf(
-			"missing %d state events IDs at event %q", len(missing), event.EventID(),
-		)
-	}
-
-	return result, nil
-}
-
 func (s *OutputRoomEventConsumer) updateStateEvent(event gomatrixserverlib.HeaderedEvent) (gomatrixserverlib.HeaderedEvent, error) {
 	var stateKey string
 	if event.StateKey() == nil {
@@ -270,17 +204,3 @@ func (s *OutputRoomEventConsumer) updateStateEvent(event gomatrixserverlib.Heade
 	event.Event, err = event.SetUnsigned(prev)
 	return event, err
 }
-
-func missingEventsFrom(events []gomatrixserverlib.HeaderedEvent, required []string) []string {
-	have := map[string]bool{}
-	for _, event := range events {
-		have[event.EventID()] = true
-	}
-	var missing []string
-	for _, eventID := range required {
-		if !have[eventID] {
-			missing = append(missing, eventID)
-		}
-	}
-	return missing
-}
diff --git a/syncapi/routing/messages.go b/syncapi/routing/messages.go
index 8c897634..de5429db 100644
--- a/syncapi/routing/messages.go
+++ b/syncapi/routing/messages.go
@@ -375,15 +375,15 @@ func (e eventsByDepth) Less(i, j int) bool {
 // Returns an error if there was an issue with retrieving the list of servers in
 // the room or sending the request.
 func (r *messagesReq) backfill(roomID string, backwardsExtremities map[string][]string, limit int) ([]gomatrixserverlib.HeaderedEvent, error) {
-	var res api.QueryBackfillResponse
-	err := r.rsAPI.QueryBackfill(context.Background(), &api.QueryBackfillRequest{
+	var res api.PerformBackfillResponse
+	err := r.rsAPI.PerformBackfill(context.Background(), &api.PerformBackfillRequest{
 		RoomID:               roomID,
 		BackwardsExtremities: backwardsExtremities,
 		Limit:                limit,
 		ServerName:           r.cfg.Matrix.ServerName,
 	}, &res)
 	if err != nil {
-		return nil, fmt.Errorf("QueryBackfill failed: %w", err)
+		return nil, fmt.Errorf("PerformBackfill failed: %w", err)
 	}
 	util.GetLogger(r.ctx).WithField("new_events", len(res.Events)).Info("Storing new events from backfill")