diff --git a/swh/storage/algos/origin.py b/swh/storage/algos/origin.py
--- a/swh/storage/algos/origin.py
+++ b/swh/storage/algos/origin.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 Optional, Iterable, Iterator, Tuple
+from typing import Iterator, List, Optional, Tuple
 
 from swh.model.model import Origin, OriginVisit, OriginVisitStatus
 from swh.storage.interface import StorageInterface
@@ -50,7 +50,7 @@
     storage: StorageInterface,
     origin_url: str,
     type: Optional[str] = None,
-    allowed_statuses: Optional[Iterable[str]] = None,
+    allowed_statuses: Optional[List[str]] = None,
     require_snapshot: bool = False,
 ) -> Optional[Tuple[OriginVisit, OriginVisitStatus]]:
     """Get the latest origin visit (and status) of an origin. Optionally, a combination of
@@ -85,6 +85,7 @@
     )
     result: Optional[Tuple[OriginVisit, OriginVisitStatus]] = None
     if visit:
+        assert visit.visit is not None
         visit_status = storage.origin_visit_status_get_latest(
             origin_url,
             visit.visit,
diff --git a/swh/storage/algos/snapshot.py b/swh/storage/algos/snapshot.py
--- a/swh/storage/algos/snapshot.py
+++ b/swh/storage/algos/snapshot.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, Optional
+from typing import List, Optional
 
 from swh.model.model import Snapshot
 
@@ -39,7 +39,7 @@
 def snapshot_get_latest(
     storage,
     origin: str,
-    allowed_statuses: Optional[Iterable[str]] = None,
+    allowed_statuses: Optional[List[str]] = None,
     branches_count: Optional[int] = None,
 ) -> Optional[Snapshot]:
     """Get the latest snapshot for the given origin, optionally only from visits that have
diff --git a/swh/storage/buffer.py b/swh/storage/buffer.py
--- a/swh/storage/buffer.py
+++ b/swh/storage/buffer.py
@@ -9,6 +9,7 @@
 from swh.core.utils import grouper
 from swh.model.model import Content, BaseModel
 from swh.storage import get_storage
+from swh.storage.interface import StorageInterface
 
 
 class BufferingProxyStorage:
@@ -36,7 +37,7 @@
     """
 
     def __init__(self, storage, min_batch_size=None):
-        self.storage = get_storage(**storage)
+        self.storage: StorageInterface = get_storage(**storage)
 
         if min_batch_size is None:
             min_batch_size = {}
@@ -67,7 +68,7 @@
             raise AttributeError(key)
         return getattr(self.storage, key)
 
-    def content_add(self, content: Iterable[Content]) -> Dict:
+    def content_add(self, content: List[Content]) -> Dict:
         """Enqueue contents to write to the storage.
 
         Following policies apply:
@@ -79,7 +80,6 @@
               threshold is hit. If it is flush content to the storage.
 
         """
-        content = list(content)
         s = self.object_add(
             content,
             object_type="content",
@@ -93,14 +93,14 @@
 
         return s
 
-    def skipped_content_add(self, content: Iterable[Content]) -> Dict:
+    def skipped_content_add(self, content: List[Content]) -> Dict:
         return self.object_add(
             content,
             object_type="skipped_content",
             keys=["sha1", "sha1_git", "sha256", "blake2s256"],
         )
 
-    def flush(self, object_types: Optional[Iterable[str]] = None) -> Dict:
+    def flush(self, object_types: Optional[List[str]] = None) -> Dict:
         summary: Dict[str, int] = self.storage.flush(object_types)
         if object_types is None:
             object_types = self.object_types
@@ -132,7 +132,7 @@
 
         return {}
 
-    def clear_buffers(self, object_types: Optional[Iterable[str]] = None) -> None:
+    def clear_buffers(self, object_types: Optional[List[str]] = None) -> None:
         """Clear objects from current buffer.
 
         WARNING:
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
@@ -146,7 +146,7 @@
 
         return summary
 
-    def content_add(self, content: Iterable[Content]) -> Dict:
+    def content_add(self, content: List[Content]) -> Dict:
         contents = [attr.evolve(c, ctime=now()) for c in content]
         return self._content_add(list(contents), with_data=True)
 
@@ -155,8 +155,8 @@
             "content_update is not supported by the Cassandra backend"
         )
 
-    def content_add_metadata(self, content: Iterable[Content]) -> Dict:
-        return self._content_add(list(content), with_data=False)
+    def content_add_metadata(self, content: List[Content]) -> Dict:
+        return self._content_add(content, with_data=False)
 
     def content_get(self, content):
         if len(content) > BULK_BLOCK_CONTENT_LEN_MAX:
@@ -280,7 +280,7 @@
                 if getattr(row, algo) == hash_:
                     yield row
 
-    def _skipped_content_add(self, contents: Iterable[SkippedContent]) -> Dict:
+    def _skipped_content_add(self, contents: List[SkippedContent]) -> Dict:
         # Filter-out content already in the database.
         contents = [
             c
@@ -305,7 +305,7 @@
 
         return {"skipped_content:add": len(contents)}
 
-    def skipped_content_add(self, content: Iterable[SkippedContent]) -> Dict:
+    def skipped_content_add(self, content: List[SkippedContent]) -> Dict:
         contents = [attr.evolve(c, ctime=now()) for c in content]
         return self._skipped_content_add(contents)
 
@@ -314,9 +314,7 @@
             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: Iterable[Directory]) -> Dict:
-        directories = list(directories)
-
+    def directory_add(self, directories: List[Directory]) -> Dict:
         # 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]
@@ -419,9 +417,7 @@
     def directory_get_random(self):
         return self._cql_runner.directory_get_random().id
 
-    def revision_add(self, revisions: Iterable[Revision]) -> Dict:
-        revisions = list(revisions)
-
+    def revision_add(self, revisions: List[Revision]) -> Dict:
         # Filter-out revisions already in the database
         missing = self.revision_missing([rev.id for rev in revisions])
         revisions = [rev for rev in revisions if rev.id in missing]
@@ -510,7 +506,7 @@
     def revision_get_random(self):
         return self._cql_runner.revision_get_random().id
 
-    def release_add(self, releases: Iterable[Release]) -> Dict:
+    def release_add(self, releases: List[Release]) -> Dict:
         to_add = []
         for rel in releases:
             if rel not in to_add:
@@ -542,8 +538,7 @@
     def release_get_random(self):
         return self._cql_runner.release_get_random().id
 
-    def snapshot_add(self, snapshots: Iterable[Snapshot]) -> Dict:
-        snapshots = list(snapshots)
+    def snapshot_add(self, snapshots: List[Snapshot]) -> Dict:
         missing = self._cql_runner.snapshot_missing([snp.id for snp in snapshots])
         snapshots = [snp for snp in snapshots if snp.id in missing]
 
@@ -685,7 +680,7 @@
 
         return results
 
-    def origin_get(self, origins: Iterable[str]) -> Iterable[Optional[Origin]]:
+    def origin_get(self, origins: List[str]) -> Iterable[Optional[Origin]]:
         return [self.origin_get_one(origin) for origin in origins]
 
     def origin_get_one(self, origin_url: str) -> Optional[Origin]:
@@ -746,15 +741,14 @@
 
         return [{"url": orig.url,} for orig in origins[offset : offset + limit]]
 
-    def origin_add(self, origins: Iterable[Origin]) -> Dict[str, int]:
-        origins = list(origins)
+    def origin_add(self, origins: List[Origin]) -> Dict[str, int]:
         to_add = [ori for ori in origins if self.origin_get_one(ori.url) is None]
         self.journal_writer.origin_add(to_add)
         for origin in to_add:
             self._cql_runner.origin_add_one(origin)
         return {"origin:add": len(to_add)}
 
-    def origin_visit_add(self, visits: Iterable[OriginVisit]) -> Iterable[OriginVisit]:
+    def origin_visit_add(self, visits: List[OriginVisit]) -> Iterable[OriginVisit]:
         for visit in visits:
             origin = self.origin_get_one(visit.origin)
             if not origin:  # Cannot add a visit without an origin
@@ -790,9 +784,7 @@
         self.journal_writer.origin_visit_status_add([visit_status])
         self._cql_runner.origin_visit_status_add_one(visit_status)
 
-    def origin_visit_status_add(
-        self, visit_statuses: Iterable[OriginVisitStatus]
-    ) -> None:
+    def origin_visit_status_add(self, visit_statuses: List[OriginVisitStatus]) -> None:
         # First round to check existence (fail early if any is ko)
         for visit_status in visit_statuses:
             origin_url = self.origin_get_one(visit_status.origin)
@@ -969,10 +961,7 @@
     def refresh_stat_counters(self):
         pass
 
-    def raw_extrinsic_metadata_add(
-        self, metadata: Iterable[RawExtrinsicMetadata]
-    ) -> None:
-        metadata = list(metadata)
+    def raw_extrinsic_metadata_add(self, metadata: List[RawExtrinsicMetadata]) -> None:
         self.journal_writer.raw_extrinsic_metadata_add(metadata)
         for metadata_entry in metadata:
             if not self._cql_runner.metadata_authority_get(
@@ -1109,8 +1098,7 @@
             "results": results,
         }
 
-    def metadata_fetcher_add(self, fetchers: Iterable[MetadataFetcher]) -> None:
-        fetchers = list(fetchers)
+    def metadata_fetcher_add(self, fetchers: List[MetadataFetcher]) -> None:
         self.journal_writer.metadata_fetcher_add(fetchers)
         for fetcher in fetchers:
             self._cql_runner.metadata_fetcher_add(
@@ -1132,8 +1120,7 @@
         else:
             return None
 
-    def metadata_authority_add(self, authorities: Iterable[MetadataAuthority]) -> None:
-        authorities = list(authorities)
+    def metadata_authority_add(self, authorities: List[MetadataAuthority]) -> None:
         self.journal_writer.metadata_authority_add(authorities)
         for authority in authorities:
             self._cql_runner.metadata_authority_add(
@@ -1155,11 +1142,11 @@
         else:
             return None
 
-    def clear_buffers(self, object_types: Optional[Iterable[str]] = None) -> None:
+    def clear_buffers(self, object_types: Optional[List[str]] = None) -> None:
         """Do nothing
 
         """
         return None
 
-    def flush(self, object_types: Optional[Iterable[str]] = None) -> Dict:
+    def flush(self, object_types: Optional[List[str]] = None) -> Dict:
         return {}
diff --git a/swh/storage/filter.py b/swh/storage/filter.py
--- a/swh/storage/filter.py
+++ b/swh/storage/filter.py
@@ -4,7 +4,7 @@
 # See top-level LICENSE file for more information
 
 
-from typing import Dict, Iterable, Set
+from typing import Dict, Iterable, List, Set
 
 from swh.model.model import (
     Content,
@@ -14,6 +14,7 @@
 )
 
 from swh.storage import get_storage
+from swh.storage.interface import StorageInterface
 
 
 class FilteringProxyStorage:
@@ -35,38 +36,34 @@
     object_types = ["content", "skipped_content", "directory", "revision"]
 
     def __init__(self, storage):
-        self.storage = get_storage(**storage)
+        self.storage: StorageInterface = get_storage(**storage)
 
     def __getattr__(self, key):
         if key == "storage":
             raise AttributeError(key)
         return getattr(self.storage, key)
 
-    def content_add(self, content: Iterable[Content]) -> Dict:
-        contents = list(content)
-        contents_to_add = self._filter_missing_contents(contents)
+    def content_add(self, content: List[Content]) -> Dict:
+        contents_to_add = self._filter_missing_contents(content)
         return self.storage.content_add(
-            x for x in contents if x.sha256 in contents_to_add
+            x for x in content if x.sha256 in contents_to_add
         )
 
-    def skipped_content_add(self, content: Iterable[SkippedContent]) -> Dict:
-        contents = list(content)
-        contents_to_add = self._filter_missing_skipped_contents(contents)
+    def skipped_content_add(self, content: List[SkippedContent]) -> Dict:
+        contents_to_add = self._filter_missing_skipped_contents(content)
         return self.storage.skipped_content_add(
-            x for x in contents if x.sha1_git is None or x.sha1_git in contents_to_add
+            x for x in content if x.sha1_git is None or x.sha1_git in contents_to_add
         )
 
-    def directory_add(self, directories: Iterable[Directory]) -> Dict:
-        directories = list(directories)
+    def directory_add(self, directories: List[Directory]) -> Dict:
         missing_ids = self._filter_missing_ids("directory", (d.id for d in directories))
         return self.storage.directory_add(d for d in directories if d.id in missing_ids)
 
-    def revision_add(self, revisions: Iterable[Revision]) -> Dict:
-        revisions = list(revisions)
+    def revision_add(self, revisions: List[Revision]) -> Dict:
         missing_ids = self._filter_missing_ids("revision", (r.id for r in revisions))
         return self.storage.revision_add(r for r in revisions if r.id in missing_ids)
 
-    def _filter_missing_contents(self, contents: Iterable[Content]) -> Set[bytes]:
+    def _filter_missing_contents(self, contents: List[Content]) -> Set[bytes]:
         """Return only the content keys missing from swh
 
         Args:
@@ -81,7 +78,7 @@
         return set(self.storage.content_missing(missing_contents, key_hash="sha256",))
 
     def _filter_missing_skipped_contents(
-        self, contents: Iterable[SkippedContent]
+        self, contents: List[SkippedContent]
     ) -> Set[bytes]:
         """Return only the content keys missing from swh
 
@@ -106,7 +103,7 @@
 
         Args:
             object_type: object type to use {revision, directory}
-            ids: Iterable of object_type ids
+            ids: List of object_type ids
 
         Returns:
             Missing ids from the storage for object_type
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
@@ -176,7 +176,7 @@
     def check_config(self, *, check_write):
         return True
 
-    def _content_add(self, contents: Iterable[Content], with_data: bool) -> Dict:
+    def _content_add(self, contents: List[Content], with_data: bool) -> Dict:
         self.journal_writer.content_add(contents)
 
         content_add = 0
@@ -220,7 +220,7 @@
 
         return summary
 
-    def content_add(self, content: Iterable[Content]) -> Dict:
+    def content_add(self, content: List[Content]) -> Dict:
         content = [attr.evolve(c, ctime=now()) for c in content]
         return self._content_add(content, with_data=True)
 
@@ -246,7 +246,7 @@
                     hash_ = new_cont.get_hash(algorithm)
                     self._content_indexes[algorithm][hash_].add(new_key)
 
-    def content_add_metadata(self, content: Iterable[Content]) -> Dict:
+    def content_add_metadata(self, content: List[Content]) -> Dict:
         return self._content_add(content, with_data=False)
 
     def content_get(self, content):
@@ -381,7 +381,7 @@
 
         return summary
 
-    def skipped_content_add(self, content: Iterable[SkippedContent]) -> Dict:
+    def skipped_content_add(self, content: List[SkippedContent]) -> Dict:
         content = [attr.evolve(c, ctime=now()) for c in content]
         return self._skipped_content_add(content)
 
@@ -399,7 +399,7 @@
             if not matches:
                 yield {algo: content[algo] for algo in DEFAULT_ALGORITHMS}
 
-    def directory_add(self, directories: Iterable[Directory]) -> Dict:
+    def directory_add(self, directories: List[Directory]) -> Dict:
         directories = [dir_ for dir_ in directories if dir_.id not in self._directories]
         self.journal_writer.directory_add(directories)
 
@@ -486,7 +486,7 @@
             first_item["target"], paths[1:], prefix + paths[0] + b"/"
         )
 
-    def revision_add(self, revisions: Iterable[Revision]) -> Dict:
+    def revision_add(self, revisions: List[Revision]) -> Dict:
         revisions = [rev for rev in revisions if rev.id not in self._revisions]
         self.journal_writer.revision_add(revisions)
 
@@ -538,7 +538,7 @@
     def revision_get_random(self):
         return random.choice(list(self._revisions))
 
-    def release_add(self, releases: Iterable[Release]) -> Dict:
+    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:
@@ -566,9 +566,9 @@
     def release_get_random(self):
         return random.choice(list(self._releases))
 
-    def snapshot_add(self, snapshots: Iterable[Snapshot]) -> Dict:
+    def snapshot_add(self, snapshots: List[Snapshot]) -> Dict:
         count = 0
-        snapshots = (snap for snap in snapshots if snap.id not in self._snapshots)
+        snapshots = [snap for snap in snapshots if snap.id not in self._snapshots]
         for snapshot in snapshots:
             self.journal_writer.snapshot_add([snapshot])
             self._snapshots[snapshot.id] = snapshot
@@ -673,7 +673,7 @@
     def origin_get_one(self, origin_url: str) -> Optional[Origin]:
         return self._origins.get(origin_url)
 
-    def origin_get(self, origins: Iterable[str]) -> Iterable[Optional[Origin]]:
+    def origin_get(self, origins: List[str]) -> Iterable[Optional[Origin]]:
         return [self.origin_get_one(origin_url) for origin_url in origins]
 
     def origin_get_by_sha1(self, sha1s):
@@ -743,8 +743,7 @@
             )
         )
 
-    def origin_add(self, origins: Iterable[Origin]) -> Dict[str, int]:
-        origins = list(origins)
+    def origin_add(self, origins: List[Origin]) -> Dict[str, int]:
         added = 0
         for origin in origins:
             if origin.url not in self._origins:
@@ -769,7 +768,7 @@
 
         return origin.url
 
-    def origin_visit_add(self, visits: Iterable[OriginVisit]) -> Iterable[OriginVisit]:
+    def origin_visit_add(self, visits: List[OriginVisit]) -> Iterable[OriginVisit]:
         for visit in visits:
             origin = self.origin_get_one(visit.origin)
             if not origin:  # Cannot add a visit without an origin
@@ -818,9 +817,7 @@
         if visit_status not in visit_statuses:
             visit_statuses.append(visit_status)
 
-    def origin_visit_status_add(
-        self, visit_statuses: Iterable[OriginVisitStatus],
-    ) -> None:
+    def origin_visit_status_add(self, visit_statuses: List[OriginVisitStatus],) -> None:
         # First round to check existence (fail early if any is ko)
         for visit_status in visit_statuses:
             origin_url = self.origin_get_one(visit_status.origin)
@@ -1018,10 +1015,7 @@
     def refresh_stat_counters(self):
         pass
 
-    def raw_extrinsic_metadata_add(
-        self, metadata: Iterable[RawExtrinsicMetadata],
-    ) -> None:
-        metadata = list(metadata)
+    def raw_extrinsic_metadata_add(self, metadata: List[RawExtrinsicMetadata],) -> None:
         self.journal_writer.raw_extrinsic_metadata_add(metadata)
         for metadata_entry in metadata:
             authority_key = self._metadata_authority_key(metadata_entry.authority)
@@ -1132,8 +1126,7 @@
             "results": results,
         }
 
-    def metadata_fetcher_add(self, fetchers: Iterable[MetadataFetcher]) -> None:
-        fetchers = list(fetchers)
+    def metadata_fetcher_add(self, fetchers: List[MetadataFetcher]) -> None:
         self.journal_writer.metadata_fetcher_add(fetchers)
         for fetcher in fetchers:
             if fetcher.metadata is None:
@@ -1151,8 +1144,7 @@
             self._metadata_fetcher_key(MetadataFetcher(name=name, version=version))
         )
 
-    def metadata_authority_add(self, authorities: Iterable[MetadataAuthority]) -> None:
-        authorities = list(authorities)
+    def metadata_authority_add(self, authorities: List[MetadataAuthority]) -> None:
         self.journal_writer.metadata_authority_add(authorities)
         for authority in authorities:
             if authority.metadata is None:
@@ -1208,11 +1200,11 @@
     def diff_revision(self, revision, track_renaming=False):
         raise NotImplementedError("InMemoryStorage.diff_revision")
 
-    def clear_buffers(self, object_types: Optional[Iterable[str]] = None) -> None:
+    def clear_buffers(self, object_types: Optional[List[str]] = None) -> None:
         """Do nothing
 
         """
         return None
 
-    def flush(self, object_types: Optional[Iterable[str]] = None) -> Dict:
+    def flush(self, object_types: Optional[List[str]] = None) -> Dict:
         return {}
diff --git a/swh/storage/interface.py b/swh/storage/interface.py
--- a/swh/storage/interface.py
+++ b/swh/storage/interface.py
@@ -39,7 +39,7 @@
         ...
 
     @remote_api_endpoint("content/add")
-    def content_add(self, content: Iterable[Content]) -> Dict:
+    def content_add(self, content: List[Content]) -> Dict:
         """Add content blobs to the storage
 
         Args:
@@ -97,7 +97,7 @@
         ...
 
     @remote_api_endpoint("content/add_metadata")
-    def content_add_metadata(self, content: Iterable[Content]) -> Dict:
+    def content_add_metadata(self, content: List[Content]) -> Dict:
         """Add content metadata to the storage (like `content_add`, but
         without inserting to the objstorage).
 
@@ -248,7 +248,7 @@
         """List content missing from storage based only on sha1.
 
         Args:
-            contents: Iterable of sha1 to check for absence.
+            contents: List of sha1 to check for absence.
 
         Returns:
             iterable: missing ids
@@ -264,7 +264,7 @@
         """List content missing from storage based only on sha1_git.
 
         Args:
-            contents (Iterable): An iterable of content id (sha1_git)
+            contents (List): An iterable of content id (sha1_git)
 
         Yields:
             missing contents sha1_git
@@ -301,7 +301,7 @@
         ...
 
     @remote_api_endpoint("content/skipped/add")
-    def skipped_content_add(self, content: Iterable[SkippedContent]) -> Dict:
+    def skipped_content_add(self, content: List[SkippedContent]) -> Dict:
         """Add contents to the skipped_content list, which contains
         (partial) information about content missing from the archive.
 
@@ -352,7 +352,7 @@
         ...
 
     @remote_api_endpoint("directory/add")
-    def directory_add(self, directories: Iterable[Directory]) -> Dict:
+    def directory_add(self, directories: List[Directory]) -> Dict:
         """Add directories to the storage
 
         Args:
@@ -434,11 +434,11 @@
         ...
 
     @remote_api_endpoint("revision/add")
-    def revision_add(self, revisions: Iterable[Revision]) -> Dict:
+    def revision_add(self, revisions: List[Revision]) -> Dict:
         """Add revisions to the storage
 
         Args:
-            revisions (Iterable[dict]): iterable of dictionaries representing
+            revisions (List[dict]): iterable of dictionaries representing
                 the individual revisions to add. Each dict has the following
                 keys:
 
@@ -538,11 +538,11 @@
         ...
 
     @remote_api_endpoint("release/add")
-    def release_add(self, releases: Iterable[Release]) -> Dict:
+    def release_add(self, releases: List[Release]) -> Dict:
         """Add releases to the storage
 
         Args:
-            releases (Iterable[dict]): iterable of dictionaries representing
+            releases (List[dict]): iterable of dictionaries representing
                 the individual releases to add. Each dict has the following
                 keys:
 
@@ -603,7 +603,7 @@
         ...
 
     @remote_api_endpoint("snapshot/add")
-    def snapshot_add(self, snapshots: Iterable[Snapshot]) -> Dict:
+    def snapshot_add(self, snapshots: List[Snapshot]) -> Dict:
         """Add snapshots to the storage.
 
         Args:
@@ -755,26 +755,24 @@
         ...
 
     @remote_api_endpoint("origin/visit/add")
-    def origin_visit_add(self, visits: Iterable[OriginVisit]) -> Iterable[OriginVisit]:
+    def origin_visit_add(self, visits: List[OriginVisit]) -> Iterable[OriginVisit]:
         """Add visits to storage. If the visits have no id, they will be created and assigned
         one. The resulted visits are visits with their visit id set.
 
         Args:
-            visits: Iterable of OriginVisit objects to add
+            visits: List of OriginVisit objects to add
 
         Raises:
             StorageArgumentException if some origin visit reference unknown origins
 
         Returns:
-            Iterable[OriginVisit] stored
+            List[OriginVisit] stored
 
         """
         ...
 
     @remote_api_endpoint("origin/visit_status/add")
-    def origin_visit_status_add(
-        self, visit_statuses: Iterable[OriginVisitStatus],
-    ) -> None:
+    def origin_visit_status_add(self, visit_statuses: List[OriginVisitStatus],) -> None:
         """Add origin visit statuses.
 
         If there is already a status for the same origin and visit id at the same
@@ -937,7 +935,7 @@
         ...
 
     @remote_api_endpoint("origin/get")
-    def origin_get(self, origins: Iterable[str]) -> Iterable[Optional[Origin]]:
+    def origin_get(self, origins: List[str]) -> Iterable[Optional[Origin]]:
         """Return origins.
 
         Args:
@@ -1044,7 +1042,7 @@
         ...
 
     @remote_api_endpoint("origin/add_multi")
-    def origin_add(self, origins: Iterable[Origin]) -> Dict[str, int]:
+    def origin_add(self, origins: List[Origin]) -> Dict[str, int]:
         """Add origins to the storage
 
         Args:
@@ -1077,9 +1075,7 @@
         ...
 
     @remote_api_endpoint("raw_extrinsic_metadata/add")
-    def raw_extrinsic_metadata_add(
-        self, metadata: Iterable[RawExtrinsicMetadata],
-    ) -> None:
+    def raw_extrinsic_metadata_add(self, metadata: List[RawExtrinsicMetadata],) -> None:
         """Add extrinsic metadata on objects (contents, directories, ...).
 
         The authority and fetcher must be known to the storage before
@@ -1125,7 +1121,7 @@
         ...
 
     @remote_api_endpoint("metadata_fetcher/add")
-    def metadata_fetcher_add(self, fetchers: Iterable[MetadataFetcher],) -> None:
+    def metadata_fetcher_add(self, fetchers: List[MetadataFetcher],) -> None:
         """Add new metadata fetchers to the storage.
 
         Their `name` and `version` together are unique identifiers of this
@@ -1157,7 +1153,7 @@
         ...
 
     @remote_api_endpoint("metadata_authority/add")
-    def metadata_authority_add(self, authorities: Iterable[MetadataAuthority]) -> None:
+    def metadata_authority_add(self, authorities: List[MetadataAuthority]) -> None:
         """Add new metadata authorities to the storage.
 
         Their `type` and `url` together are unique identifiers of this
@@ -1242,7 +1238,7 @@
         ...
 
     @remote_api_endpoint("clear/buffer")
-    def clear_buffers(self, object_types: Optional[Iterable[str]] = None) -> None:
+    def clear_buffers(self, object_types: Optional[List[str]] = None) -> None:
         """For backend storages (pg, storage, in-memory), this is a noop operation. For proxy
         storages (especially filter, buffer), this is an operation which cleans internal
         state.
@@ -1250,7 +1246,7 @@
         """
 
     @remote_api_endpoint("flush")
-    def flush(self, object_types: Optional[Iterable[str]] = None) -> Dict:
+    def flush(self, object_types: Optional[List[str]] = None) -> Dict:
         """For backend storages (pg, storage, in-memory), this is expected to be a noop
         operation. For proxy storages (especially buffer), this is expected to trigger
         actual writes to the backend.
diff --git a/swh/storage/retry.py b/swh/storage/retry.py
--- a/swh/storage/retry.py
+++ b/swh/storage/retry.py
@@ -6,7 +6,7 @@
 import logging
 import traceback
 
-from typing import Dict, Iterable, Optional
+from typing import Dict, Iterable, List, Optional
 
 from tenacity import (
     retry,
@@ -29,6 +29,7 @@
 
 from swh.storage import get_storage
 from swh.storage.exc import StorageArgumentException
+from swh.storage.interface import StorageInterface
 
 
 logger = logging.getLogger(__name__)
@@ -85,7 +86,7 @@
     """
 
     def __init__(self, storage):
-        self.storage = get_storage(**storage)
+        self.storage: StorageInterface = get_storage(**storage)
 
     def __getattr__(self, key):
         if key == "storage":
@@ -93,55 +94,53 @@
         return getattr(self.storage, key)
 
     @swh_retry
-    def content_add(self, content: Iterable[Content]) -> Dict:
+    def content_add(self, content: List[Content]) -> Dict:
         return self.storage.content_add(content)
 
     @swh_retry
-    def content_add_metadata(self, content: Iterable[Content]) -> Dict:
+    def content_add_metadata(self, content: List[Content]) -> Dict:
         return self.storage.content_add_metadata(content)
 
     @swh_retry
-    def skipped_content_add(self, content: Iterable[SkippedContent]) -> Dict:
+    def skipped_content_add(self, content: List[SkippedContent]) -> Dict:
         return self.storage.skipped_content_add(content)
 
     @swh_retry
-    def origin_visit_add(self, visits: Iterable[OriginVisit]) -> Iterable[OriginVisit]:
+    def origin_visit_add(self, visits: List[OriginVisit]) -> Iterable[OriginVisit]:
         return self.storage.origin_visit_add(visits)
 
     @swh_retry
-    def metadata_fetcher_add(self, fetchers: Iterable[MetadataFetcher],) -> None:
+    def metadata_fetcher_add(self, fetchers: List[MetadataFetcher],) -> None:
         return self.storage.metadata_fetcher_add(fetchers)
 
     @swh_retry
-    def metadata_authority_add(self, authorities: Iterable[MetadataAuthority]) -> None:
+    def metadata_authority_add(self, authorities: List[MetadataAuthority]) -> None:
         return self.storage.metadata_authority_add(authorities)
 
     @swh_retry
-    def raw_extrinsic_metadata_add(
-        self, metadata: Iterable[RawExtrinsicMetadata],
-    ) -> None:
+    def raw_extrinsic_metadata_add(self, metadata: List[RawExtrinsicMetadata],) -> None:
         return self.storage.raw_extrinsic_metadata_add(metadata)
 
     @swh_retry
-    def directory_add(self, directories: Iterable[Directory]) -> Dict:
+    def directory_add(self, directories: List[Directory]) -> Dict:
         return self.storage.directory_add(directories)
 
     @swh_retry
-    def revision_add(self, revisions: Iterable[Revision]) -> Dict:
+    def revision_add(self, revisions: List[Revision]) -> Dict:
         return self.storage.revision_add(revisions)
 
     @swh_retry
-    def release_add(self, releases: Iterable[Release]) -> Dict:
+    def release_add(self, releases: List[Release]) -> Dict:
         return self.storage.release_add(releases)
 
     @swh_retry
-    def snapshot_add(self, snapshots: Iterable[Snapshot]) -> Dict:
+    def snapshot_add(self, snapshots: List[Snapshot]) -> Dict:
         return self.storage.snapshot_add(snapshots)
 
-    def clear_buffers(self, object_types: Optional[Iterable[str]] = None) -> None:
+    def clear_buffers(self, object_types: Optional[List[str]] = None) -> None:
         return self.storage.clear_buffers(object_types)
 
-    def flush(self, object_types: Optional[Iterable[str]] = None) -> Dict:
+    def flush(self, object_types: Optional[List[str]] = None) -> Dict:
         """Specific case for buffer proxy storage failing to flush data
 
         """
diff --git a/swh/storage/storage.py b/swh/storage/storage.py
--- a/swh/storage/storage.py
+++ b/swh/storage/storage.py
@@ -204,7 +204,7 @@
 
     @timed
     @process_metrics
-    def content_add(self, content: Iterable[Content]) -> Dict:
+    def content_add(self, content: List[Content]) -> Dict:
         ctime = now()
 
         contents = [attr.evolve(c, ctime=ctime) for c in content]
@@ -247,14 +247,11 @@
     @timed
     @process_metrics
     @db_transaction()
-    def content_add_metadata(
-        self, content: Iterable[Content], db=None, cur=None
-    ) -> Dict:
-        contents = list(content)
+    def content_add_metadata(self, content: List[Content], db=None, cur=None) -> Dict:
         missing = self.content_missing(
-            (c.to_dict() for c in contents), key_hash="sha1_git", db=db, cur=cur,
+            (c.to_dict() for c in content), key_hash="sha1_git", db=db, cur=cur,
         )
-        contents = [c for c in contents if c.sha1_git in missing]
+        contents = [c for c in content if c.sha1_git in missing]
 
         self.journal_writer.content_add_metadata(contents)
         self._content_add_metadata(db, cur, contents)
@@ -393,7 +390,7 @@
 
         return d
 
-    def _skipped_content_add_metadata(self, db, cur, content: Iterable[SkippedContent]):
+    def _skipped_content_add_metadata(self, db, cur, content: List[SkippedContent]):
         origin_ids = db.origin_id_get_by_url([cont.origin for cont in content], cur=cur)
         content = [
             attr.evolve(c, origin=origin_id)
@@ -414,7 +411,7 @@
     @process_metrics
     @db_transaction()
     def skipped_content_add(
-        self, content: Iterable[SkippedContent], db=None, cur=None
+        self, content: List[SkippedContent], db=None, cur=None
     ) -> Dict:
         ctime = now()
         content = [attr.evolve(c, ctime=ctime) for c in content]
@@ -451,10 +448,7 @@
     @timed
     @process_metrics
     @db_transaction()
-    def directory_add(
-        self, directories: Iterable[Directory], db=None, cur=None
-    ) -> Dict:
-        directories = list(directories)
+    def directory_add(self, directories: List[Directory], db=None, cur=None) -> Dict:
         summary = {"directory:add": 0}
 
         dirs = set()
@@ -540,8 +534,7 @@
     @timed
     @process_metrics
     @db_transaction()
-    def revision_add(self, revisions: Iterable[Revision], db=None, cur=None) -> Dict:
-        revisions = list(revisions)
+    def revision_add(self, revisions: List[Revision], db=None, cur=None) -> Dict:
         summary = {"revision:add": 0}
 
         revisions_missing = set(
@@ -628,8 +621,7 @@
     @timed
     @process_metrics
     @db_transaction()
-    def release_add(self, releases: Iterable[Release], db=None, cur=None) -> Dict:
-        releases = list(releases)
+    def release_add(self, releases: List[Release], db=None, cur=None) -> Dict:
         summary = {"release:add": 0}
 
         release_ids = set(release.id for release in releases)
@@ -679,7 +671,7 @@
     @timed
     @process_metrics
     @db_transaction()
-    def snapshot_add(self, snapshots: Iterable[Snapshot], db=None, cur=None) -> Dict:
+    def snapshot_add(self, snapshots: List[Snapshot], db=None, cur=None) -> Dict:
         created_temp_table = False
 
         count = 0
@@ -799,7 +791,7 @@
     @timed
     @db_transaction()
     def origin_visit_add(
-        self, visits: Iterable[OriginVisit], db=None, cur=None
+        self, visits: List[OriginVisit], db=None, cur=None
     ) -> Iterable[OriginVisit]:
         for visit in visits:
             origin = self.origin_get([visit.origin], db=db, cur=cur)[0]
@@ -847,7 +839,7 @@
     @timed
     @db_transaction()
     def origin_visit_status_add(
-        self, visit_statuses: Iterable[OriginVisitStatus], db=None, cur=None,
+        self, visit_statuses: List[OriginVisitStatus], db=None, cur=None,
     ) -> None:
         # First round to check existence (fail early if any is ko)
         for visit_status in visit_statuses:
@@ -995,10 +987,9 @@
     @timed
     @db_transaction(statement_timeout=500)
     def origin_get(
-        self, origins: Iterable[str], db=None, cur=None
+        self, origins: List[str], db=None, cur=None
     ) -> Iterable[Optional[Origin]]:
-        origin_urls = list(origins)
-        rows = db.origin_get_by_url(origin_urls, cur)
+        rows = db.origin_get_by_url(origins, cur)
         result: List[Optional[Origin]] = []
         for row in rows:
             origin_d = dict(zip(db.origin_cols, row))
@@ -1073,9 +1064,7 @@
     @timed
     @process_metrics
     @db_transaction()
-    def origin_add(
-        self, origins: Iterable[Origin], db=None, cur=None
-    ) -> Dict[str, int]:
+    def origin_add(self, origins: List[Origin], db=None, cur=None) -> Dict[str, int]:
         urls = [o.url for o in origins]
         known_origins = set(url for (url,) in db.origin_get_by_url(urls, cur))
         # use lists here to keep origins sorted; some tests depend on this
@@ -1115,7 +1104,7 @@
 
     @db_transaction()
     def raw_extrinsic_metadata_add(
-        self, metadata: Iterable[RawExtrinsicMetadata], db, cur,
+        self, metadata: List[RawExtrinsicMetadata], db, cur,
     ) -> None:
         metadata = list(metadata)
         self.journal_writer.raw_extrinsic_metadata_add(metadata)
@@ -1255,7 +1244,7 @@
     @timed
     @db_transaction()
     def metadata_fetcher_add(
-        self, fetchers: Iterable[MetadataFetcher], db=None, cur=None
+        self, fetchers: List[MetadataFetcher], db=None, cur=None
     ) -> None:
         fetchers = list(fetchers)
         self.journal_writer.metadata_fetcher_add(fetchers)
@@ -1284,7 +1273,7 @@
     @timed
     @db_transaction()
     def metadata_authority_add(
-        self, authorities: Iterable[MetadataAuthority], db=None, cur=None
+        self, authorities: List[MetadataAuthority], db=None, cur=None
     ) -> None:
         authorities = list(authorities)
         self.journal_writer.metadata_authority_add(authorities)
@@ -1325,13 +1314,13 @@
     def diff_revision(self, revision, track_renaming=False):
         return diff.diff_revision(self, revision, track_renaming)
 
-    def clear_buffers(self, object_types: Optional[Iterable[str]] = None) -> None:
+    def clear_buffers(self, object_types: Optional[List[str]] = None) -> None:
         """Do nothing
 
         """
         return None
 
-    def flush(self, object_types: Optional[Iterable[str]] = None) -> Dict:
+    def flush(self, object_types: Optional[List[str]] = None) -> Dict:
         return {}
 
     def _get_authority_id(self, authority: MetadataAuthority, db, cur):
diff --git a/swh/storage/tests/test_storage.py b/swh/storage/tests/test_storage.py
--- a/swh/storage/tests/test_storage.py
+++ b/swh/storage/tests/test_storage.py
@@ -187,22 +187,6 @@
         swh_storage.refresh_stat_counters()
         assert swh_storage.stat_counters()["content"] == 1
 
-    def test_content_add_from_generator(self, swh_storage, sample_data):
-        cont = sample_data.content
-
-        def _cnt_gen():
-            yield cont
-
-        actual_result = swh_storage.content_add(_cnt_gen())
-
-        assert actual_result == {
-            "content:add": 1,
-            "content:add:bytes": cont.length,
-        }
-
-        swh_storage.refresh_stat_counters()
-        assert swh_storage.stat_counters()["content"] == 1
-
     def test_content_add_from_lazy_content(self, swh_storage, sample_data):
         cont = sample_data.content
         lazy_content = LazyContent.from_dict(cont.to_dict())
@@ -677,22 +661,6 @@
         swh_storage.refresh_stat_counters()
         assert swh_storage.stat_counters()["directory"] == 1
 
-    def test_directory_add_from_generator(self, swh_storage, sample_data):
-        directory = sample_data.directories[1]
-
-        def _dir_gen():
-            yield directory
-
-        actual_result = swh_storage.directory_add(directories=_dir_gen())
-        assert actual_result == {"directory:add": 1}
-
-        assert list(swh_storage.journal_writer.journal.objects) == [
-            ("directory", directory)
-        ]
-
-        swh_storage.refresh_stat_counters()
-        assert swh_storage.stat_counters()["directory"] == 1
-
     def test_directory_add_twice(self, swh_storage, sample_data):
         directory = sample_data.directories[1]
 
@@ -881,18 +849,6 @@
         swh_storage.refresh_stat_counters()
         assert swh_storage.stat_counters()["revision"] == 1
 
-    def test_revision_add_from_generator(self, swh_storage, sample_data):
-        revision = sample_data.revision
-
-        def _rev_gen():
-            yield revision
-
-        actual_result = swh_storage.revision_add(_rev_gen())
-        assert actual_result == {"revision:add": 1}
-
-        swh_storage.refresh_stat_counters()
-        assert swh_storage.stat_counters()["revision"] == 1
-
     def test_revision_add_twice(self, swh_storage, sample_data):
         revision, revision2 = sample_data.revisions[:2]
 
@@ -1062,24 +1018,6 @@
         swh_storage.refresh_stat_counters()
         assert swh_storage.stat_counters()["release"] == 2
 
-    def test_release_add_from_generator(self, swh_storage, sample_data):
-        release, release2 = sample_data.releases[:2]
-
-        def _rel_gen():
-            yield release
-            yield release2
-
-        actual_result = swh_storage.release_add(_rel_gen())
-        assert actual_result == {"release:add": 2}
-
-        assert list(swh_storage.journal_writer.journal.objects) == [
-            ("release", release),
-            ("release", release2),
-        ]
-
-        swh_storage.refresh_stat_counters()
-        assert swh_storage.stat_counters()["release"] == 2
-
     def test_release_add_no_author_date(self, swh_storage, sample_data):
         full_release = sample_data.release
 
@@ -1187,26 +1125,6 @@
         swh_storage.refresh_stat_counters()
         assert swh_storage.stat_counters()["origin"] == 2
 
-    def test_origin_add_from_generator(self, swh_storage, sample_data):
-        origin, origin2 = sample_data.origins[:2]
-
-        def _ori_gen():
-            yield origin
-            yield origin2
-
-        stats = swh_storage.origin_add(_ori_gen())
-        assert stats == {"origin:add": 2}
-
-        actual_origins = swh_storage.origin_get([origin.url, origin2.url])
-        assert actual_origins == [origin, origin2]
-
-        assert set(swh_storage.journal_writer.journal.objects) == set(
-            [("origin", origin), ("origin", origin2),]
-        )
-
-        swh_storage.refresh_stat_counters()
-        assert swh_storage.stat_counters()["origin"] == 2
-
     def test_origin_add_twice(self, swh_storage, sample_data):
         origin, origin2 = sample_data.origins[:2]
 
@@ -2377,18 +2295,6 @@
         swh_storage.refresh_stat_counters()
         assert swh_storage.stat_counters()["snapshot"] == 2
 
-    def test_snapshot_add_many_from_generator(self, swh_storage, sample_data):
-        snapshot, _, complete_snapshot = sample_data.snapshots[:3]
-
-        def _snp_gen():
-            yield from [snapshot, complete_snapshot]
-
-        actual_result = swh_storage.snapshot_add(_snp_gen())
-        assert actual_result == {"snapshot:add": 2}
-
-        swh_storage.refresh_stat_counters()
-        assert swh_storage.stat_counters()["snapshot"] == 2
-
     def test_snapshot_add_many_incremental(self, swh_storage, sample_data):
         snapshot, _, complete_snapshot = sample_data.snapshots[:3]