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
@@ -57,6 +57,7 @@
 )
 from swh.model.hashutil import DEFAULT_ALGORITHMS, hash_to_bytes, hash_to_hex
 
+from swh.storage.cassandra import CassandraStorage
 from swh.storage.cassandra.model import BaseRow
 from swh.storage.interface import (
     ListOrder,
@@ -219,7 +220,7 @@
         )
 
 
-class InMemoryStorage:
+class InMemoryStorage(CassandraStorage):
     def __init__(self, journal_writer=None):
         self.reset()
         self.journal_writer = JournalWriter(journal_writer)
@@ -505,29 +506,10 @@
             if id not in self._directories:
                 yield id
 
-    def _join_dentry_to_content(self, dentry: Dict[str, Any]) -> Dict[str, Any]:
-        keys = (
-            "status",
-            "sha1",
-            "sha1_git",
-            "sha256",
-            "length",
-        )
-        ret = dict.fromkeys(keys)
-        ret.update(dentry)
-        if ret["type"] == "file":
-            # TODO: Make it able to handle more than one content
-            contents = self.content_find({"sha1_git": ret["target"]})
-            if contents:
-                content = contents[0]
-                for key in keys:
-                    ret[key] = getattr(content, key)
-        return ret
-
     def _directory_ls(self, directory_id, recursive, prefix=b""):
         if directory_id in self._directories:
             for entry in self._directories[directory_id].entries:
-                ret = self._join_dentry_to_content(entry.to_dict())
+                ret = self._join_dentry_to_content(entry)
                 ret["name"] = prefix + ret["name"]
                 ret["dir_id"] = directory_id
                 yield ret
@@ -610,7 +592,7 @@
             else:
                 yield None
 
-    def _get_parent_revs(
+    def __get_parent_revs(
         self, rev_id: Sha1Git, seen: Set[Sha1Git], limit: Optional[int]
     ) -> Iterable[Dict[str, Any]]:
         if limit and len(seen) >= limit:
@@ -620,14 +602,14 @@
         seen.add(rev_id)
         yield self._revisions[rev_id].to_dict()
         for parent in self._revisions[rev_id].parents:
-            yield from self._get_parent_revs(parent, seen, limit)
+            yield from self.__get_parent_revs(parent, seen, limit)
 
     def revision_log(
         self, revisions: List[Sha1Git], limit: Optional[int] = None
     ) -> Iterable[Optional[Dict[str, Any]]]:
         seen: Set[Sha1Git] = set()
         for rev_id in revisions:
-            yield from self._get_parent_revs(rev_id, seen, limit)
+            yield from self.__get_parent_revs(rev_id, seen, limit)
 
     def revision_shortlog(
         self, revisions: List[Sha1Git], limit: Optional[int] = None
diff --git a/swh/storage/writer.py b/swh/storage/writer.py
--- a/swh/storage/writer.py
+++ b/swh/storage/writer.py
@@ -3,7 +3,7 @@
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
-from typing import Iterable
+from typing import Any, Dict, Iterable
 
 from attr import evolve
 
@@ -57,7 +57,7 @@
         contents = [evolve(item, data=None) for item in contents]
         self.write_additions("content", contents)
 
-    def content_update(self, contents: Iterable[Content]) -> None:
+    def content_update(self, contents: Iterable[Dict[str, Any]]) -> None:
         if self.journal:
             raise NotImplementedError("content_update is not supported by the journal.")