diff --git a/swh/indexer/storage/__init__.py b/swh/indexer/storage/__init__.py
--- a/swh/indexer/storage/__init__.py
+++ b/swh/indexer/storage/__init__.py
@@ -33,6 +33,7 @@
     OriginIntrinsicMetadataRow,
     RevisionIntrinsicMetadataRow,
 )
+from .writer import JournalWriter
 
 INDEXER_CFG_KEY = "indexer_storage"
 
@@ -121,12 +122,13 @@
 
     """
 
-    def __init__(self, db, min_pool_conns=1, max_pool_conns=10):
+    def __init__(self, db, min_pool_conns=1, max_pool_conns=10, journal_writer=None):
         """
         Args:
             db_conn: either a libpq connection string, or a psycopg2 connection
 
         """
+        self._writer = JournalWriter(self.indexer_configuration_get, journal_writer)
         try:
             if isinstance(db, psycopg2.extensions.connection):
                 self._pool = None
diff --git a/swh/indexer/storage/in_memory.py b/swh/indexer/storage/in_memory.py
--- a/swh/indexer/storage/in_memory.py
+++ b/swh/indexer/storage/in_memory.py
@@ -41,9 +41,12 @@
     OriginIntrinsicMetadataRow,
     RevisionIntrinsicMetadataRow,
 )
+from .writer import JournalWriter
 
 SHA1_DIGEST_SIZE = 160
 
+ToolId = int
+
 
 def _transform_tool(tool):
     return {
@@ -64,7 +67,6 @@
     return tuple(sorted(d.items()))
 
 
-ToolId = int
 TValue = TypeVar("TValue", bound=BaseRow)
 
 
@@ -74,11 +76,13 @@
     _data: Dict[Sha1, Dict[Tuple, Dict[str, Any]]]
     _tools_per_id: Dict[Sha1, Set[ToolId]]
 
-    def __init__(self, row_class: Type[TValue], tools):
+    def __init__(self, obj_type: str, row_class: Type[TValue], tools, journal_writer):
         self.row_class = row_class
+        self._obj_type = obj_type
         self._tools = tools
         self._sorted_ids = SortedList[bytes, Sha1]()
         self._data = defaultdict(dict)
+        self._journal_writer = journal_writer
         self._tools_per_id = defaultdict(set)
 
     def _key_from_dict(self, d) -> Tuple:
@@ -210,6 +214,7 @@
         """
         data = list(data)
         check_id_duplicates(data)
+        self._journal_writer.write_additions(self._obj_type, data)
         count = 0
         for obj in data:
             item = obj.to_dict()
@@ -231,6 +236,7 @@
 
         """
         deleted = 0
+        self._journal_writer.write_deletions(self._obj_type, entries)
         for entry in entries:
             (id_, tool_id) = (entry["id"], entry["indexer_configuration_id"])
             if tool_id in self._tools_per_id[id_]:
@@ -246,18 +252,23 @@
 class IndexerStorage:
     """In-memory SWH indexer storage."""
 
-    def __init__(self):
+    def __init__(self, journal_writer=None):
         self._tools = {}
-        self._mimetypes = SubStorage(ContentMimetypeRow, self._tools)
-        self._languages = SubStorage(ContentLanguageRow, self._tools)
-        self._content_ctags = SubStorage(ContentCtagsRow, self._tools)
-        self._licenses = SubStorage(ContentLicenseRow, self._tools)
-        self._content_metadata = SubStorage(ContentMetadataRow, self._tools)
+        tool_getter = self._tools.__getitem__
+        self._writer = JournalWriter(tool_getter, journal_writer)
+        args = (self._tools, self._writer)
+        self._mimetypes = SubStorage("mimetype", ContentMimetypeRow, *args)
+        self._languages = SubStorage("language", ContentLanguageRow, *args)
+        self._content_ctags = SubStorage("content_ctag", ContentCtagsRow, *args)
+        self._licenses = SubStorage("license", ContentLicenseRow, *args)
+        self._content_metadata = SubStorage(
+            "content_metadata", ContentMetadataRow, *args
+        )
         self._revision_intrinsic_metadata = SubStorage(
-            RevisionIntrinsicMetadataRow, self._tools
+            "revision_intrinsic_metadata", RevisionIntrinsicMetadataRow, *args
         )
         self._origin_intrinsic_metadata = SubStorage(
-            OriginIntrinsicMetadataRow, self._tools
+            "origin_intrinsic_metadata", OriginIntrinsicMetadataRow, *args
         )
 
     def check_config(self, *, check_write):
diff --git a/swh/indexer/storage/writer.py b/swh/indexer/storage/writer.py
new file mode 100644
--- /dev/null
+++ b/swh/indexer/storage/writer.py
@@ -0,0 +1,61 @@
+# Copyright (C) 2020 The Software Heritage developers
+# See the AUTHORS file at the top-level directory of this distribution
+# License: GNU General Public License version 3, or any later version
+# See top-level LICENSE file for more information
+
+from typing import Dict, Iterable
+
+import attr
+
+try:
+    from swh.journal.writer import get_journal_writer
+except ImportError:
+    get_journal_writer = None  # type: ignore
+    # mypy limitation, see https://github.com/python/mypy/issues/1153
+
+
+class JournalWriter:
+    """Journal writer storage collaborator. It's in charge of adding objects to
+    the journal.
+
+    """
+
+    def __init__(self, tool_getter, journal_writer):
+        self._tool_getter = tool_getter
+        if journal_writer:
+            if get_journal_writer is None:
+                raise EnvironmentError(
+                    "You need the swh.journal package to use the "
+                    "journal_writer feature"
+                )
+            self.journal = get_journal_writer(**journal_writer)
+        else:
+            self.journal = None
+
+    def write_additions(self, obj_type, entries) -> None:
+        if self.journal:
+            # usually, all the additions in a batch are from the same indexer,
+            # so this cache allows doing a single query for all the entries.
+            tool_cache = {}
+
+            for entry in entries:
+                # get the tool used to generate this addition
+                tool_id = entry.indexer_configuration_id
+                if tool_id not in tool_cache:
+                    tool_cache[tool_id] = self._tool_getter(tool_id)
+                entry = attr.evolve(
+                    entry, tool=tool_cache[tool_id], indexer_configuration_id=None
+                )
+
+                # write to kafka
+                self.journal.write_addition(obj_type, entry)
+
+    def write_deletions(self, obj_type, entries) -> None:
+        if self.journal:
+            raise NotImplementedError("deletions are not supported by the journal.")
+
+    def revision_intrinsic_metadata_add(self, metadata: Iterable[Dict]) -> None:
+        self.write_additions("revision_intrinsic_metadata", metadata)
+
+    def origin_intrinsic_metadata_add(self, metadata: Iterable[Dict]) -> None:
+        self.write_additions("origin_intrinsic_metadata", metadata)
diff --git a/swh/indexer/tests/storage/conftest.py b/swh/indexer/tests/storage/conftest.py
--- a/swh/indexer/tests/storage/conftest.py
+++ b/swh/indexer/tests/storage/conftest.py
@@ -73,4 +73,8 @@
 
 @pytest.fixture
 def swh_indexer_storage(swh_indexer_storage_postgresql):
-    return get_indexer_storage("local", db=swh_indexer_storage_postgresql.dsn)
+    return get_indexer_storage(
+        "local",
+        db=swh_indexer_storage_postgresql.dsn,
+        journal_writer={"cls": "memory",},
+    )
diff --git a/swh/indexer/tests/storage/test_api_client.py b/swh/indexer/tests/storage/test_api_client.py
--- a/swh/indexer/tests/storage/test_api_client.py
+++ b/swh/indexer/tests/storage/test_api_client.py
@@ -14,7 +14,11 @@
 
 @pytest.fixture
 def app(swh_indexer_storage_postgresql):
-    server.storage = get_indexer_storage("local", db=swh_indexer_storage_postgresql.dsn)
+    server.storage = get_indexer_storage(
+        "local",
+        db=swh_indexer_storage_postgresql.dsn,
+        journal_writer={"cls": "memory",},
+    )
     return server.app
 
 
diff --git a/swh/indexer/tests/storage/test_in_memory.py b/swh/indexer/tests/storage/test_in_memory.py
--- a/swh/indexer/tests/storage/test_in_memory.py
+++ b/swh/indexer/tests/storage/test_in_memory.py
@@ -12,4 +12,4 @@
 
 @pytest.fixture
 def swh_indexer_storage():
-    return get_indexer_storage("memory")
+    return get_indexer_storage("memory", journal_writer={"cls": "memory",})