diff --git a/swh/storage/cassandra/storage.py b/swh/storage/cassandra/storage.py
--- a/swh/storage/cassandra/storage.py
+++ b/swh/storage/cassandra/storage.py
@@ -558,10 +558,12 @@
 
         return {"release:add": len(to_add)}
 
-    def release_missing(self, releases):
+    def release_missing(self, releases: List[Sha1Git]) -> Iterable[Sha1Git]:
         return self._cql_runner.release_missing(releases)
 
-    def release_get(self, releases):
+    def release_get(
+        self, releases: List[Sha1Git]
+    ) -> Iterable[Optional[Dict[str, Any]]]:
         rows = self._cql_runner.release_get(releases)
         rels = {}
         for row in rows:
diff --git a/swh/storage/in_memory.py b/swh/storage/in_memory.py
--- a/swh/storage/in_memory.py
+++ b/swh/storage/in_memory.py
@@ -582,10 +582,12 @@
 
         return {"release:add": len(to_add)}
 
-    def release_missing(self, releases):
+    def release_missing(self, releases: List[Sha1Git]) -> Iterable[Sha1Git]:
         yield from (rel for rel in releases if rel not in self._releases)
 
-    def release_get(self, releases):
+    def release_get(
+        self, releases: List[Sha1Git]
+    ) -> Iterable[Optional[Dict[str, Any]]]:
         for rel_id in releases:
             if rel_id in self._releases:
                 yield self._releases[rel_id].to_dict()
diff --git a/swh/storage/interface.py b/swh/storage/interface.py
--- a/swh/storage/interface.py
+++ b/swh/storage/interface.py
@@ -606,20 +606,22 @@
         ...
 
     @remote_api_endpoint("release/missing")
-    def release_missing(self, releases):
-        """List releases missing from storage
+    def release_missing(self, releases: List[Sha1Git]) -> Iterable[Sha1Git]:
+        """List missing release ids from storage
 
         Args:
-            releases: an iterable of release ids
+            releases: release ids
 
-        Returns:
+        Yields:
             a list of missing release ids
 
         """
         ...
 
     @remote_api_endpoint("release")
-    def release_get(self, releases):
+    def release_get(
+        self, releases: List[Sha1Git]
+    ) -> Iterable[Optional[Dict[str, Any]]]:
         """Given a list of sha1, return the releases's information
 
         Args:
diff --git a/swh/storage/storage.py b/swh/storage/storage.py
--- a/swh/storage/storage.py
+++ b/swh/storage/storage.py
@@ -680,7 +680,9 @@
 
     @timed
     @db_transaction_generator()
-    def release_missing(self, releases, db=None, cur=None):
+    def release_missing(
+        self, releases: List[Sha1Git], db=None, cur=None
+    ) -> Iterable[Sha1Git]:
         if not releases:
             return
 
@@ -689,7 +691,9 @@
 
     @timed
     @db_transaction_generator(statement_timeout=500)
-    def release_get(self, releases, db=None, cur=None):
+    def release_get(
+        self, releases: List[Sha1Git], db=None, cur=None
+    ) -> Iterable[Optional[Dict[str, Any]]]:
         for release in db.release_get_from_list(releases, cur):
             data = converters.db_to_release(dict(zip(db.release_get_cols, release)))
             yield data if data["target_type"] else None