diff --git a/swh/journal/pytest_plugin.py b/swh/journal/pytest_plugin.py
--- a/swh/journal/pytest_plugin.py
+++ b/swh/journal/pytest_plugin.py
@@ -13,7 +13,7 @@
 from confluent_kafka.admin import AdminClient
 import pytest
 
-from swh.journal.serializers import kafka_to_key, kafka_to_value, object_key, pprint_key
+from swh.journal.serializers import kafka_to_key, kafka_to_value, pprint_key
 from swh.journal.tests.journal_data import TEST_OBJECTS
 
 
@@ -69,7 +69,7 @@
 
     """
     for object_type, known_objects in TEST_OBJECTS.items():
-        known_keys = [object_key(object_type, obj) for obj in known_objects]
+        known_keys = [obj.unique_key() for obj in known_objects]
 
         if not consumed_messages[object_type]:
             return
diff --git a/swh/journal/serializers.py b/swh/journal/serializers.py
--- a/swh/journal/serializers.py
+++ b/swh/journal/serializers.py
@@ -3,15 +3,15 @@
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
-from typing import Any, Dict, Union, overload
+from typing import Any, Union
 
 import msgpack
 
 from swh.core.api.serializers import msgpack_dumps, msgpack_loads
-from swh.model.hashutil import DEFAULT_ALGORITHMS
 from swh.model.model import (
     Content,
     Directory,
+    KeyType,
     MetadataAuthority,
     MetadataFetcher,
     Origin,
@@ -39,82 +39,6 @@
     Snapshot,
 ]
 
-KeyType = Union[Dict[str, str], Dict[str, bytes], bytes]
-
-
-# these @overload'ed versions of the object_key method aim at helping mypy figuring
-# the correct type-ing.
-@overload
-def object_key(
-    object_type: str, object_: Union[Content, Directory, Revision, Release, Snapshot]
-) -> bytes:
-    ...
-
-
-@overload
-def object_key(
-    object_type: str, object_: Union[Origin, SkippedContent]
-) -> Dict[str, bytes]:
-    ...
-
-
-@overload
-def object_key(
-    object_type: str,
-    object_: Union[
-        MetadataAuthority,
-        MetadataFetcher,
-        OriginVisit,
-        OriginVisitStatus,
-        RawExtrinsicMetadata,
-    ],
-) -> Dict[str, str]:
-    ...
-
-
-def object_key(object_type: str, object_) -> KeyType:
-    if object_type in ("revision", "release", "directory", "snapshot"):
-        return object_.id
-    elif object_type == "content":
-        return object_.sha1  # TODO: use a dict of hashes
-    elif object_type == "skipped_content":
-        return {hash: getattr(object_, hash) for hash in DEFAULT_ALGORITHMS}
-    elif object_type == "origin":
-        return {"url": object_.url}
-    elif object_type == "origin_visit":
-        return {
-            "origin": object_.origin,
-            "date": str(object_.date),
-        }
-    elif object_type == "origin_visit_status":
-        return {
-            "origin": object_.origin,
-            "visit": str(object_.visit),
-            "date": str(object_.date),
-        }
-    elif object_type == "metadata_authority":
-        return {
-            "type": object_.type.value,
-            "url": object_.url,
-        }
-    elif object_type == "metadata_fetcher":
-        return {
-            "name": object_.name,
-            "version": object_.version,
-        }
-    elif object_type == "raw_extrinsic_metadata":
-        return {
-            "type": object_.type.value,
-            "id": str(object_.id),
-            "authority_type": object_.authority.type.value,
-            "authority_url": object_.authority.url,
-            "discovery_date": str(object_.discovery_date),
-            "fetcher_name": object_.fetcher.name,
-            "fetcher_version": object_.fetcher.version,
-        }
-    else:
-        raise ValueError("Unknown object type: %s." % object_type)
-
 
 def stringify_key_item(k: str, v: Union[str, bytes]) -> str:
     """Turn the item of a dict key into a string"""
diff --git a/swh/journal/tests/test_serializers.py b/swh/journal/tests/test_serializers.py
--- a/swh/journal/tests/test_serializers.py
+++ b/swh/journal/tests/test_serializers.py
@@ -30,18 +30,11 @@
         assert key == serializers.key_to_kafka(d)
 
 
-def test_get_key():
-    """Test whether get_key works on all our objects"""
-    for object_type, objects in TEST_OBJECTS.items():
-        for obj in objects:
-            assert serializers.object_key(object_type, obj) is not None
-
-
 def test_pprint_key():
     """Test whether get_key works on all our objects"""
     for object_type, objects in TEST_OBJECTS.items():
         for obj in objects:
-            key = serializers.object_key(object_type, obj)
+            key = obj.unique_key()
             pprinted_key = serializers.pprint_key(key)
             assert isinstance(pprinted_key, str)
 
@@ -66,7 +59,7 @@
     ]
     for object_type, objects in TEST_OBJECTS.items():
         for obj in objects:
-            key = serializers.object_key(object_type, obj)
+            key = obj.unique_key()
             keys.append(key)
 
     for key in keys:
diff --git a/swh/journal/writer/kafka.py b/swh/journal/writer/kafka.py
--- a/swh/journal/writer/kafka.py
+++ b/swh/journal/writer/kafka.py
@@ -13,7 +13,6 @@
     KeyType,
     ModelObject,
     key_to_kafka,
-    object_key,
     pprint_key,
     value_to_kafka,
 )
@@ -206,7 +205,7 @@
 
     def _write_addition(self, object_type: str, object_: ModelObject) -> None:
         """Write a single object to the journal"""
-        key = object_key(object_type, object_)
+        key = object_.unique_key()
 
         if self.anonymize:
             anon_object_ = object_.anonymize()