diff --git a/swh/journal/serializers.py b/swh/journal/serializers.py
--- a/swh/journal/serializers.py
+++ b/swh/journal/serializers.py
@@ -3,14 +3,58 @@
 # License: GNU General Public License version 3, or any later version
 # See top-level LICENSE file for more information
 
+import datetime
+from enum import Enum
 from typing import Any, Union
 
 import msgpack
 
-from swh.core.api.serializers import msgpack_dumps, msgpack_loads
 from swh.model.model import KeyType
 
 
+class MsgpackExtTypeCodes(Enum):
+    LONG_INT = 1
+    LONG_NEG_INT = 2
+
+
+# this as been copied from swh.core.api.serializer
+# TODO refactor swh.core to make this function available
+def _msgpack_encode_int(value):
+    # needed because msgpack will not handle long integers with more than 64 bits
+    # which we unfortunately happen to have to deal with from time to time
+    if value > 0:
+        code = MsgpackExtTypeCodes.LONG_INT.value
+    else:
+        code = MsgpackExtTypeCodes.LONG_NEG_INT.value
+        value = -value
+    length, rem = divmod(value.bit_length(), 8)
+    if rem:
+        length += 1
+    return msgpack.ExtType(code, int.to_bytes(value, length, "big"))
+
+
+def msgpack_ext_encode_types(obj):
+    if isinstance(obj, int):
+        return _msgpack_encode_int(obj)
+    return obj
+
+
+def msgpack_ext_hook(code, data):
+    if code == MsgpackExtTypeCodes.LONG_INT.value:
+        return int.from_bytes(data, "big")
+    if code == MsgpackExtTypeCodes.LONG_NEG_INT.value:
+        return -int.from_bytes(data, "big")
+
+    raise ValueError("Unknown msgpack extended code %s" % code)
+
+
+# for BW compat
+def decode_types_bw(obj):
+    if set(obj.keys()) == {b"d", b"swhtype"} and obj[b"swhtype"] == "datetime":
+        return datetime.datetime.fromisoformat(obj[b"d"])
+    return obj
+
+
 def stringify_key_item(k: str, v: Union[str, bytes]) -> str:
     """Turn the item of a dict key into a string"""
     if isinstance(v, str):
@@ -49,12 +93,24 @@
 
 def value_to_kafka(value: Any) -> bytes:
     """Serialize some data for storage in kafka"""
-    return msgpack_dumps(value)
+    return msgpack.packb(
+        value,
+        use_bin_type=True,
+        datetime=True,  # encode datetime as msgpack.Timestamp
+        default=msgpack_ext_encode_types,
+    )
 
 
 def kafka_to_value(kafka_value: bytes) -> Any:
     """Deserialize some data stored in kafka"""
-    value = msgpack_loads(kafka_value)
+    value = msgpack.unpackb(
+        kafka_value,
+        raw=False,
+        object_hook=decode_types_bw,
+        ext_hook=msgpack_ext_hook,
+        strict_map_key=False,
+        timestamp=3,  # convert Timestamp in datetime objects (tz UTC)
+    )
     return ensure_tuples(value)