diff --git a/changelog.d/18939.misc b/changelog.d/18939.misc
new file mode 100644
index 000000000..6cfae2cea
--- /dev/null
+++ b/changelog.d/18939.misc
@@ -0,0 +1 @@
+Reduce overall number of calls to `_get_e2e_cross_signing_signatures_for_devices` by increasing the batch size of devices the query is called with, reducing DB load.
diff --git a/synapse/storage/databases/main/end_to_end_keys.py b/synapse/storage/databases/main/end_to_end_keys.py
index cc389d158..2e9f62075 100644
--- a/synapse/storage/databases/main/end_to_end_keys.py
+++ b/synapse/storage/databases/main/end_to_end_keys.py
@@ -354,7 +354,10 @@ class EndToEndKeyWorkerStore(EndToEndKeyBackgroundStore, CacheInvalidationWorker
             if d is not None and d.keys is not None
         )
 
-        for batch in batch_iter(signature_query, 50):
+        # 1000 is an arbitrary batch size. It helped performance on a very
+        # large-scale deployment (matrix.org), but has not been tested against
+        # any other setup.
+        for batch in batch_iter(signature_query, 1000):
             cross_sigs_result = (
                 await self._get_e2e_cross_signing_signatures_for_devices(batch)
             )