diff --git a/changelog.d/17191.misc b/changelog.d/17191.misc
new file mode 100644
index 00000000000..bd55eeaa33c
--- /dev/null
+++ b/changelog.d/17191.misc
@@ -0,0 +1 @@
+Improve performance of calculating device lists changes in `/sync`.
diff --git a/synapse/handlers/sync.py b/synapse/handlers/sync.py
index 8ff45a3353b..0bef58351c5 100644
--- a/synapse/handlers/sync.py
+++ b/synapse/handlers/sync.py
@@ -1803,38 +1803,13 @@ async def _generate_sync_entry_for_device_list(
 
         # Step 1a, check for changes in devices of users we share a room
         # with
-        #
-        # We do this in two different ways depending on what we have cached.
-        # If we already have a list of all the user that have changed since
-        # the last sync then it's likely more efficient to compare the rooms
-        # they're in with the rooms the syncing user is in.
-        #
-        # If we don't have that info cached then we get all the users that
-        # share a room with our user and check if those users have changed.
-        cache_result = self.store.get_cached_device_list_changes(
-            since_token.device_list_key
-        )
-        if cache_result.hit:
-            changed_users = cache_result.entities
-
-            result = await self.store.get_rooms_for_users(changed_users)
-
-            for changed_user_id, entries in result.items():
-                # Check if the changed user shares any rooms with the user,
-                # or if the changed user is the syncing user (as we always
-                # want to include device list updates of their own devices).
-                if user_id == changed_user_id or any(
-                    rid in joined_rooms for rid in entries
-                ):
-                    users_that_have_changed.add(changed_user_id)
-        else:
-            users_that_have_changed = (
-                await self._device_handler.get_device_changes_in_shared_rooms(
-                    user_id,
-                    sync_result_builder.joined_room_ids,
-                    from_token=since_token,
-                )
+        users_that_have_changed = (
+            await self._device_handler.get_device_changes_in_shared_rooms(
+                user_id,
+                sync_result_builder.joined_room_ids,
+                from_token=since_token,
             )
+        )
 
         # Step 1b, check for newly joined rooms
         for room_id in newly_joined_rooms:
diff --git a/synapse/storage/databases/main/devices.py b/synapse/storage/databases/main/devices.py
index 8dbcb3f5a05..d98f0593bce 100644
--- a/synapse/storage/databases/main/devices.py
+++ b/synapse/storage/databases/main/devices.py
@@ -70,10 +70,7 @@
 from synapse.util import json_decoder, json_encoder
 from synapse.util.caches.descriptors import cached, cachedList
 from synapse.util.caches.lrucache import LruCache
-from synapse.util.caches.stream_change_cache import (
-    AllEntitiesChangedResult,
-    StreamChangeCache,
-)
+from synapse.util.caches.stream_change_cache import StreamChangeCache
 from synapse.util.cancellation import cancellable
 from synapse.util.iterutils import batch_iter
 from synapse.util.stringutils import shortstr
@@ -832,16 +829,6 @@ async def get_cached_devices_for_user(
         )
         return {device[0]: db_to_json(device[1]) for device in devices}
 
-    def get_cached_device_list_changes(
-        self,
-        from_key: int,
-    ) -> AllEntitiesChangedResult:
-        """Get set of users whose devices have changed since `from_key`, or None
-        if that information is not in our cache.
-        """
-
-        return self._device_list_stream_cache.get_all_entities_changed(from_key)
-
     @cancellable
     async def get_all_devices_changed(
         self,
@@ -1475,7 +1462,7 @@ async def get_device_list_changes_in_rooms(
 
         sql = """
             SELECT DISTINCT user_id FROM device_lists_changes_in_room
-            WHERE {clause} AND stream_id >= ?
+            WHERE {clause} AND stream_id > ?
         """
 
         def _get_device_list_changes_in_rooms_txn(