diff --git a/synapse/storage/devices.py b/synapse/storage/devices.py
index 79a58df591..111bfb3d64 100644
--- a/synapse/storage/devices.py
+++ b/synapse/storage/devices.py
@@ -512,17 +512,9 @@ class DeviceWorkerStore(SQLBaseStore):
         return results
 
 
-class DeviceStore(DeviceWorkerStore, BackgroundUpdateStore):
+class DeviceBackgroundUpdateStore(BackgroundUpdateStore):
     def __init__(self, db_conn, hs):
-        super(DeviceStore, self).__init__(db_conn, hs)
-
-        # Map of (user_id, device_id) -> bool. If there is an entry that implies
-        # the device exists.
-        self.device_id_exists_cache = Cache(
-            name="device_id_exists", keylen=2, max_entries=10000
-        )
-
-        self._clock.looping_call(self._prune_old_outbound_device_pokes, 60 * 60 * 1000)
+        super(DeviceBackgroundUpdateStore, self).__init__(db_conn, hs)
 
         self.register_background_index_update(
             "device_lists_stream_idx",
@@ -555,6 +547,31 @@ class DeviceStore(DeviceWorkerStore, BackgroundUpdateStore):
             self._drop_device_list_streams_non_unique_indexes,
         )
 
+    @defer.inlineCallbacks
+    def _drop_device_list_streams_non_unique_indexes(self, progress, batch_size):
+        def f(conn):
+            txn = conn.cursor()
+            txn.execute("DROP INDEX IF EXISTS device_lists_remote_cache_id")
+            txn.execute("DROP INDEX IF EXISTS device_lists_remote_extremeties_id")
+            txn.close()
+
+        yield self.runWithConnection(f)
+        yield self._end_background_update(DROP_DEVICE_LIST_STREAMS_NON_UNIQUE_INDEXES)
+        return 1
+
+
+class DeviceStore(DeviceWorkerStore, DeviceBackgroundUpdateStore):
+    def __init__(self, db_conn, hs):
+        super(DeviceStore, self).__init__(db_conn, hs)
+
+        # Map of (user_id, device_id) -> bool. If there is an entry that implies
+        # the device exists.
+        self.device_id_exists_cache = Cache(
+            name="device_id_exists", keylen=2, max_entries=10000
+        )
+
+        self._clock.looping_call(self._prune_old_outbound_device_pokes, 60 * 60 * 1000)
+
     @defer.inlineCallbacks
     def store_device(self, user_id, device_id, initial_device_display_name):
         """Ensure the given device is known; add it to the store if not
@@ -910,15 +927,3 @@ class DeviceStore(DeviceWorkerStore, BackgroundUpdateStore):
             "_prune_old_outbound_device_pokes",
             _prune_txn,
         )
-
-    @defer.inlineCallbacks
-    def _drop_device_list_streams_non_unique_indexes(self, progress, batch_size):
-        def f(conn):
-            txn = conn.cursor()
-            txn.execute("DROP INDEX IF EXISTS device_lists_remote_cache_id")
-            txn.execute("DROP INDEX IF EXISTS device_lists_remote_extremeties_id")
-            txn.close()
-
-        yield self.runWithConnection(f)
-        yield self._end_background_update(DROP_DEVICE_LIST_STREAMS_NON_UNIQUE_INDEXES)
-        return 1