diff --git a/swh/web/browse/snapshot_context.py b/swh/web/browse/snapshot_context.py
--- a/swh/web/browse/snapshot_context.py
+++ b/swh/web/browse/snapshot_context.py
@@ -268,8 +268,8 @@
             continue
         for branch in revision_to_branch[revision["id"]]:
             _add_branch_info(branch, revision)
-        for release in revision_to_release[revision["id"]]:
-            releases[release]["directory"] = revision["directory"]
+        for release_id in revision_to_release[revision["id"]]:
+            releases[release_id]["directory"] = revision["directory"]
 
     for branch_alias, branch_target in branch_aliases.items():
         if branch_target in branches:
diff --git a/swh/web/common/service.py b/swh/web/common/service.py
--- a/swh/web/common/service.py
+++ b/swh/web/common/service.py
@@ -446,7 +446,7 @@
     return converters.from_directory_entry(queried_dir)
 
 
-def lookup_release(release_sha1_git):
+def lookup_release(release_sha1_git: str) -> Dict[str, Any]:
     """Return information about the release with sha1 release_sha1_git.
 
     Args:
@@ -462,19 +462,20 @@
     sha1_git_bin = _to_sha1_bin(release_sha1_git)
     release = _first_element(storage.release_get([sha1_git_bin]))
     if not release:
-        raise NotFoundExc("Release with sha1_git %s not found." % release_sha1_git)
-    return converters.from_release(release)
+        raise NotFoundExc(f"Release with sha1_git {release_sha1_git} not found.")
+    return converters.from_release(release.to_dict())
 
 
-def lookup_release_multiple(sha1_git_list):
-    """Return information about the revisions identified with
+def lookup_release_multiple(sha1_git_list) -> Iterator[Dict[str, Any]]:
+    """Return information about the releases identified with
     their sha1_git identifiers.
 
     Args:
-        sha1_git_list: A list of revision sha1_git identifiers
+        sha1_git_list: A list of release sha1_git identifiers
 
     Returns:
-        Release information as dict.
+        Iterator of Release metadata information as dict. Unknown releases are
+        filtered out.
 
     Raises:
         ValueError if the identifier provided is not of sha1 nature.
@@ -482,7 +483,9 @@
     """
     sha1_bin_list = [_to_sha1_bin(sha1_git) for sha1_git in sha1_git_list]
     releases = storage.release_get(sha1_bin_list) or []
-    return (converters.from_release(r) for r in releases)
+    for r in releases:
+        if r is not None:
+            yield converters.from_release(r.to_dict())
 
 
 def lookup_revision(rev_sha1_git):
diff --git a/swh/web/tests/conftest.py b/swh/web/tests/conftest.py
--- a/swh/web/tests/conftest.py
+++ b/swh/web/tests/conftest.py
@@ -19,7 +19,7 @@
 
 from swh.model.hashutil import ALGORITHMS, hash_to_bytes
 from swh.web.common import converters
-from swh.web.common.typing import OriginVisitInfo
+from swh.web.common.typing import OriginVisitInfo, ReleaseMetadata
 from swh.web.tests.data import get_tests_data, override_storages
 from swh.storage.algos.origin import origin_get_latest_visit_status
 from swh.storage.algos.snapshot import snapshot_get_all_branches, snapshot_get_latest
@@ -205,10 +205,10 @@
         )
         return list(dir_content)
 
-    def release_get(self, rel_id):
+    def release_get(self, rel_id: str) -> ReleaseMetadata:
         rel_id_bytes = hash_to_bytes(rel_id)
-        rel_data = next(self.storage.release_get([rel_id_bytes]))
-        return converters.from_release(rel_data)
+        rel_data = self.storage.release_get([rel_id_bytes])[0]
+        return converters.from_release(rel_data.to_dict() if rel_data else None)
 
     def revision_get(self, rev_id):
         rev_id_bytes = hash_to_bytes(rev_id)
diff --git a/swh/web/tests/data.py b/swh/web/tests/data.py
--- a/swh/web/tests/data.py
+++ b/swh/web/tests/data.py
@@ -227,8 +227,8 @@
             if target_type == "revision":
                 revisions.add(branch_data.target)
             elif target_type == "release":
-                release = next(storage.release_get([branch_data.target]))
-                revisions.add(release["target"])
+                release = storage.release_get([branch_data.target])[0]
+                revisions.add(release.target)
                 releases.add(hash_to_hex(branch_data.target))
 
         for rev_log in storage.revision_shortlog(set(revisions)):
diff --git a/swh/web/tests/strategies.py b/swh/web/tests/strategies.py
--- a/swh/web/tests/strategies.py
+++ b/swh/web/tests/strategies.py
@@ -342,7 +342,7 @@
     into the test archive.
     """
     return sha1().filter(
-        lambda s: next(get_tests_data()["storage"].release_get([s])) is None
+        lambda s: get_tests_data()["storage"].release_get([s])[0] is None
     )