diff --git a/roomserver/internal/input/input.go b/roomserver/internal/input/input.go
index 404bc742..a1bb63a1 100644
--- a/roomserver/internal/input/input.go
+++ b/roomserver/internal/input/input.go
@@ -19,7 +19,6 @@ import (
 	"context"
 	"encoding/json"
 	"sync"
-	"time"
 
 	"github.com/Shopify/sarama"
 	"github.com/matrix-org/dendrite/internal/hooks"
@@ -28,7 +27,6 @@ import (
 	"github.com/matrix-org/dendrite/roomserver/storage"
 	"github.com/matrix-org/gomatrixserverlib"
 	log "github.com/sirupsen/logrus"
-	"go.uber.org/atomic"
 )
 
 type Inputer struct {
@@ -38,7 +36,7 @@ type Inputer struct {
 	ACLs                 *acls.ServerACLs
 	OutputRoomEventTopic string
 
-	workers sync.Map // room ID -> *inputWorker
+	latestEventsMutexes sync.Map // room ID -> sync.Mutex
 }
 
 type inputTask struct {
@@ -48,30 +46,6 @@ type inputTask struct {
 	err   error // written back by worker, only safe to read when all tasks are done
 }
 
-type inputWorker struct {
-	r       *Inputer
-	running atomic.Bool
-	input   chan *inputTask
-}
-
-// Guarded by a CAS on w.running
-func (w *inputWorker) start() {
-	defer w.running.Store(false)
-	for {
-		select {
-		case task := <-w.input:
-			hooks.Run(hooks.KindNewEventReceived, task.event.Event)
-			_, task.err = w.r.processRoomEvent(task.ctx, task.event)
-			if task.err == nil {
-				hooks.Run(hooks.KindNewEventPersisted, task.event.Event)
-			}
-			task.wg.Done()
-		case <-time.After(time.Second * 5):
-			return
-		}
-	}
-}
-
 // WriteOutputEvents implements OutputRoomEventWriter
 func (r *Inputer) WriteOutputEvents(roomID string, updates []api.OutputEvent) error {
 	messages := make([]*sarama.ProducerMessage, len(updates))
@@ -127,37 +101,21 @@ func (r *Inputer) InputRoomEvents(
 	wg.Add(len(request.InputRoomEvents))
 	tasks := make([]*inputTask, len(request.InputRoomEvents))
 
-	for i, e := range request.InputRoomEvents {
-		// Work out if we are running per-room workers or if we're just doing
-		// it on a global basis (e.g. SQLite).
-		roomID := "global"
-		if r.DB.SupportsConcurrentRoomInputs() {
-			roomID = e.Event.RoomID()
-		}
-
-		// Look up the worker, or create it if it doesn't exist. This channel
-		// is buffered to reduce the chance that we'll be blocked by another
-		// room - the channel will be quite small as it's just pointer types.
-		w, _ := r.workers.LoadOrStore(roomID, &inputWorker{
-			r:     r,
-			input: make(chan *inputTask, 32),
-		})
-		worker := w.(*inputWorker)
-
-		// Create a task. This contains the input event and a reference to
-		// the wait group, so that the worker can notify us when this specific
-		// task has been finished.
+	for i := range request.InputRoomEvents {
+		wg.Add(1)
 		tasks[i] = &inputTask{
 			ctx:   context.Background(),
 			event: &request.InputRoomEvents[i],
 			wg:    wg,
 		}
-
-		// Send the task to the worker.
-		if worker.running.CAS(false, true) {
-			go worker.start()
-		}
-		worker.input <- tasks[i]
+		go func(task *inputTask) {
+			hooks.Run(hooks.KindNewEventReceived, task.event.Event)
+			_, task.err = r.processRoomEvent(task.ctx, task.event)
+			if task.err == nil {
+				hooks.Run(hooks.KindNewEventPersisted, task.event.Event)
+			}
+			task.wg.Done()
+		}(tasks[i])
 	}
 
 	// Wait for all of the workers to return results about our tasks.
diff --git a/roomserver/internal/input/input_latest_events.go b/roomserver/internal/input/input_latest_events.go
index c9264a27..0551ed52 100644
--- a/roomserver/internal/input/input_latest_events.go
+++ b/roomserver/internal/input/input_latest_events.go
@@ -19,6 +19,7 @@ package input
 import (
 	"context"
 	"fmt"
+	"sync"
 
 	"github.com/matrix-org/dendrite/internal/sqlutil"
 	"github.com/matrix-org/dendrite/roomserver/api"
@@ -55,6 +56,11 @@ func (r *Inputer) updateLatestEvents(
 	transactionID *api.TransactionID,
 	rewritesState bool,
 ) (err error) {
+	v, _ := r.latestEventsMutexes.LoadOrStore(roomInfo.RoomNID, &sync.Mutex{})
+	mutex := v.(*sync.Mutex)
+	mutex.Lock()
+	defer mutex.Unlock()
+
 	updater, err := r.DB.GetLatestEventsForUpdate(ctx, *roomInfo)
 	if err != nil {
 		return fmt.Errorf("r.DB.GetLatestEventsForUpdate: %w", err)