diff --git a/CONTRIBUTORS b/CONTRIBUTORS
--- a/CONTRIBUTORS
+++ b/CONTRIBUTORS
@@ -1,3 +1,4 @@
 Daniele Serafini
 Ishan Bhanuka
+Kumar Shivendu
 Quentin Campos
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
@@ -20,6 +20,7 @@
     Set,
     Tuple,
     Union,
+    ValuesView,
 )
 
 import attr
@@ -191,8 +192,9 @@
 
         return summary
 
-    def content_add(self, content: List[Content]) -> Dict:
-        contents = [attr.evolve(c, ctime=now()) for c in content]
+    def content_add(self, contents: Union[List[Content], ValuesView[Content]]) -> Dict:
+        contents = {c.swhid(): c for c in contents}.values()
+        contents = [attr.evolve(c, ctime=now()) for c in contents]
         return self._content_add(list(contents), with_data=True)
 
     def content_update(
@@ -353,7 +355,10 @@
             if not self._cql_runner.skipped_content_get_from_pk(content):
                 yield {algo: content[algo] for algo in DEFAULT_ALGORITHMS}
 
-    def directory_add(self, directories: List[Directory]) -> Dict:
+    def directory_add(
+        self, directories: Union[ValuesView[Directory], List[Directory]]
+    ) -> Dict:
+        directories = {d.swhid(): d for d in directories}.values()
         # Filter out directories that are already inserted.
         missing = self.directory_missing([dir_.id for dir_ in directories])
         directories = [dir_ for dir_ in directories if dir_.id in missing]
@@ -477,8 +482,11 @@
         assert directory, "Could not find any directory"
         return directory.id
 
-    def revision_add(self, revisions: List[Revision]) -> Dict:
+    def revision_add(
+        self, revisions: Union[ValuesView[Revision], List[Revision]]
+    ) -> Dict:
         # Filter-out revisions already in the database
+        revisions = {r.swhid(): r for r in revisions}.values()
         missing = self.revision_missing([rev.id for rev in revisions])
         revisions = [rev for rev in revisions if rev.id in missing]
         self.journal_writer.revision_add(revisions)
@@ -588,21 +596,18 @@
         assert revision, "Could not find any revision"
         return revision.id
 
-    def release_add(self, releases: List[Release]) -> Dict:
-        to_add = []
-        for rel in releases:
-            if rel not in to_add:
-                to_add.append(rel)
-        missing = set(self.release_missing([rel.id for rel in to_add]))
-        to_add = [rel for rel in to_add if rel.id in missing]
+    def release_add(self, releases: Union[ValuesView[Release], List[Release]]) -> Dict:
+        releases = {r.swhid(): r for r in releases}.values()
+        missing = set(self.release_missing([rel.id for rel in releases]))
+        releases = [rel for rel in releases if rel.id in missing]
 
-        self.journal_writer.release_add(to_add)
+        self.journal_writer.release_add(releases)
 
-        for release in to_add:
+        for release in releases:
             if release:
                 self._cql_runner.release_add_one(converters.release_to_db(release))
 
-        return {"release:add": len(to_add)}
+        return {"release:add": len(releases)}
 
     def release_missing(self, releases: List[Sha1Git]) -> Iterable[Sha1Git]:
         return self._cql_runner.release_missing(releases)
@@ -621,7 +626,10 @@
         assert release, "Could not find any release"
         return release.id
 
-    def snapshot_add(self, snapshots: List[Snapshot]) -> Dict:
+    def snapshot_add(
+        self, snapshots: Union[ValuesView[Snapshot], List[Snapshot]]
+    ) -> Dict:
+        snapshots = {s.swhid(): s for s in snapshots}.values()
         missing = self._cql_runner.snapshot_missing([snp.id for snp in snapshots])
         snapshots = [snp for snp in snapshots if snp.id in missing]
 
@@ -891,7 +899,10 @@
             "The Cassandra backend does not implement origin_count"
         )
 
-    def origin_add(self, origins: List[Origin]) -> Dict[str, int]:
+    def origin_add(
+        self, origins: Union[ValuesView[Origin], List[Origin]]
+    ) -> Dict[str, int]:
+        origins = {o.swhid(): o for o in origins}.values()
         to_add = [ori for ori in origins if self.origin_get_one(ori.url) is None]
         # keep only one occurrence of each given origin while keeping the list
         # sorted as originally given