diff --git a/synapse/crypto/keyring.py b/synapse/crypto/keyring.py
index 69310d90351c..afd75287a686 100644
--- a/synapse/crypto/keyring.py
+++ b/synapse/crypto/keyring.py
@@ -154,8 +154,11 @@ def __init__(
 
         if key_fetchers is None:
             key_fetchers = (
+                # Fetch keys from the database.
                 StoreKeyFetcher(hs),
+                # Fetch keys from a configured Perspectives server.
                 PerspectivesKeyFetcher(hs),
+                # Fetch keys from the origin server directly.
                 ServerKeyFetcher(hs),
             )
         self._key_fetchers = key_fetchers
@@ -279,6 +282,10 @@ async def process_request(self, verify_request: VerifyJsonRequest) -> None:
 
         key_ids_to_find = set(verify_request.key_ids) - found_keys.keys()
         if key_ids_to_find:
+            # We're still missing some keys. Consult each of our `KeyFetcher` instances
+            # (stored in `self._key_fetchers`) to try and find them. Key fetch attempts
+            # are queued via `self._server_queue` below.
+
             # Add the keys we need to verify to the queue for retrieval. We queue
             # up requests for the same server so we don't end up with many in flight
             # requests for the same keys.