diff --git a/h/celery.py b/h/celery.py
index ab3af120ca5..685e48bbb00 100644
--- a/h/celery.py
+++ b/h/celery.py
@@ -74,6 +74,7 @@
     # task's @app.task() arguments.
     task_time_limit=240,
     imports=(
+        "h.tasks.annotations",
         "h.tasks.cleanup",
         "h.tasks.indexer",
         "h.tasks.mailer",
diff --git a/h/tasks/annotations.py b/h/tasks/annotations.py
new file mode 100644
index 00000000000..9586ec69667
--- /dev/null
+++ b/h/tasks/annotations.py
@@ -0,0 +1,55 @@
+from sqlalchemy import func, insert
+
+from h.celery import celery, get_task_logger
+from h.models import Annotation, AnnotationModeration, AnnotationSlim, Group, User
+
+log = get_task_logger(__name__)
+
+
+@celery.task
+def fill_annotation_slim(batch_size=1000):
+    """Task to fill the new AnnotationSlim table in batches."""
+    # pylint: disable=no-member
+    db = celery.request.db
+
+    annotations = (
+        db.query(
+            Annotation.id.label("pubid"),
+            Annotation.created,
+            Annotation.updated,
+            Annotation.deleted,
+            Annotation.shared,
+            Annotation.document_id,
+            Group.id.label("group_id"),
+            User.id.label("user_id"),
+            AnnotationModeration.id.is_not(None).label("moderated"),
+        )
+        .join(Group, Group.pubid == Annotation.groupid)
+        .join(
+            User,
+            User.username
+            == func.split_part(func.split_part(Annotation.userid, "@", 1), ":", 2),
+        )
+        .outerjoin(AnnotationSlim)
+        .outerjoin(AnnotationModeration)
+        .where(AnnotationSlim.id.is_(None))
+        .order_by(Annotation.created.asc())
+        .limit(batch_size)
+    ).cte("annotations")
+
+    db.execute(
+        insert(AnnotationSlim).from_select(
+            [
+                annotations.c.pubid,
+                annotations.c.created,
+                annotations.c.updated,
+                annotations.c.deleted,
+                annotations.c.shared,
+                annotations.c.document_id,
+                annotations.c.group_id,
+                annotations.c.user_id,
+                annotations.c.moderated,
+            ],
+            annotations,
+        )
+    )
diff --git a/tests/h/tasks/annotations_test.py b/tests/h/tasks/annotations_test.py
new file mode 100644
index 00000000000..2d688f0c0bd
--- /dev/null
+++ b/tests/h/tasks/annotations_test.py
@@ -0,0 +1,51 @@
+import pytest
+
+from h.models import Annotation, AnnotationSlim
+from h.tasks.annotations import fill_annotation_slim
+
+
+class TestFillPKAndUserId:
+    AUTHORITY_1 = "AUTHORITY_1"
+    AUTHORITY_2 = "AUTHORITY_2"
+
+    USERNAME_1 = "USERNAME_1"
+    USERNAME_2 = "USERNAME_2"
+
+    def test_it(self, factories, db_session):
+        author = factories.User(authority=self.AUTHORITY_1, username=self.USERNAME_1)
+
+        annos = factories.Annotation.create_batch(
+            10,
+            userid=author.userid,
+        )
+        factories.Annotation.create_batch(5)
+
+        fill_annotation_slim(batch_size=10)
+
+        assert db_session.query(AnnotationSlim).count() == 10
+        assert (
+            db_session.query(Annotation)
+            .outerjoin(AnnotationSlim)
+            .filter(AnnotationSlim.id.is_(None))
+            .count()
+            == 5
+        )
+
+        # Refresh data for the annotations
+        _ = [db_session.refresh(anno) for anno in annos]
+
+        for anno in annos:
+            assert anno.slim.pubid == anno.id
+            assert anno.slim.created == anno.created
+            assert anno.slim.updated == anno.updated
+            assert anno.slim.deleted == anno.deleted
+            assert anno.slim.shared == anno.shared
+            assert anno.slim.document_id == anno.document_id
+            assert anno.slim.group_id == anno.group.id
+            assert anno.slim.user_id == author.id
+
+    @pytest.fixture(autouse=True)
+    def celery(self, patch, db_session):
+        cel = patch("h.tasks.annotations.celery", autospec=False)
+        cel.request.db = db_session
+        return cel