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
@@ -38,7 +38,6 @@
 from swh.model.model import (
     Content,
     SkippedContent,
-    Release,
     Snapshot,
     OriginVisit,
     OriginVisitStatus,
@@ -58,6 +57,7 @@
     DirectoryRow,
     DirectoryEntryRow,
     ObjectCountRow,
+    ReleaseRow,
     RevisionRow,
     RevisionParentRow,
     SkippedContentRow,
@@ -234,6 +234,7 @@
         self._directory_entries = Table(DirectoryEntryRow)
         self._revisions = Table(RevisionRow)
         self._revision_parents = Table(RevisionParentRow)
+        self._releases = Table(RevisionRow)
         self._stat_counters = defaultdict(int)
 
     def increment_counter(self, object_type: str, nb: int):
@@ -404,7 +405,24 @@
     ##########################
 
     def release_missing(self, ids: List[bytes]) -> List[bytes]:
-        return ids
+        missing = []
+        for id_ in ids:
+            if self._releases.get_from_primary_key((id_,)) is None:
+                missing.append(id_)
+        return missing
+
+    def release_add_one(self, release: ReleaseRow) -> None:
+        self._releases.insert(release)
+        self.increment_counter("release", 1)
+
+    def release_get(self, release_ids: List[str]) -> Iterable[ReleaseRow]:
+        for id_ in release_ids:
+            row = self._releases.get_from_primary_key((id_,))
+            if row:
+                yield row
+
+    def release_get_random(self) -> Optional[ReleaseRow]:
+        return self._releases.get_random()
 
 
 class InMemoryStorage(CassandraStorage):
@@ -416,7 +434,6 @@
 
     def reset(self):
         self._cql_runner = InMemoryCqlRunner()
-        self._releases = {}
         self._snapshots = {}
         self._origins = {}
         self._origins_by_sha1 = {}
@@ -459,38 +476,6 @@
     def check_config(self, *, check_write: bool) -> bool:
         return True
 
-    def release_add(self, releases: List[Release]) -> Dict:
-        to_add = []
-        for rel in releases:
-            if rel.id not in self._releases and rel not in to_add:
-                to_add.append(rel)
-        self.journal_writer.release_add(to_add)
-
-        for rel in to_add:
-            if rel.author:
-                self._person_add(rel.author)
-            self._objects[rel.id].append(("release", rel.id))
-            self._releases[rel.id] = rel
-
-        self._cql_runner.increment_counter("release", len(to_add))
-
-        return {"release:add": len(to_add)}
-
-    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: 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()
-            else:
-                yield None
-
-    def release_get_random(self) -> Sha1Git:
-        return random.choice(list(self._releases))
-
     def snapshot_add(self, snapshots: List[Snapshot]) -> Dict:
         count = 0
         snapshots = [snap for snap in snapshots if snap.id not in self._snapshots]
@@ -595,13 +580,6 @@
     def snapshot_get_random(self) -> Sha1Git:
         return random.choice(list(self._snapshots))
 
-    def object_find_by_sha1_git(self, ids: List[Sha1Git]) -> Dict[Sha1Git, List[Dict]]:
-        ret = super().object_find_by_sha1_git(ids)
-        for id_ in ids:
-            objs = self._objects.get(id_, [])
-            ret[id_].extend([{"sha1_git": id_, "type": obj[0],} for obj in objs])
-        return ret
-
     def _convert_origin(self, t):
         if t is None:
             return None
@@ -1143,14 +1121,6 @@
         else:
             raise TypeError("origin must be a string.")
 
-    def _person_add(self, person):
-        key = ("person", person.fullname)
-        if key not in self._objects:
-            self._persons[person.fullname] = person
-            self._objects[key].append(key)
-
-        return self._persons[person.fullname]
-
     @staticmethod
     def _metadata_fetcher_key(fetcher: MetadataFetcher) -> FetcherKey:
         return (fetcher.name, fetcher.version)