diff --git a/swh/provenance/mongo/backend.py b/swh/provenance/mongo/backend.py
--- a/swh/provenance/mongo/backend.py
+++ b/swh/provenance/mongo/backend.py
@@ -8,6 +8,7 @@
 from typing import Any, Dict, Generator, Iterable, List, Optional, Set, Union
 
 from bson import ObjectId
+from pymongo import UpdateOne
 import pymongo.database
 
 from swh.model.model import Sha1Git
@@ -19,39 +20,43 @@
     RelationType,
     RevisionData,
 )
+from .entity import Entity
 
 
 class ProvenanceStorageMongoDb:
     def __init__(self, db: pymongo.database.Database):
         self.db = db
 
+    def _format_data(self, data: Union[Iterable[Sha1Git], Dict[Sha1Git, datetime]]):
+        return data if isinstance(data, dict) else dict.fromkeys(data)
+
+    def _generate_date_upserts(self, sha1, date):
+        ts = datetime.timestamp(date) if date is not None else None
+        # update only those with date either as None or later than the given one
+        return UpdateOne(
+            {"$and": [{"sha1": sha1}, {"$or": [{"ts": None}, {"ts": {"$gt": ts}}]}]},
+            {"$set": {"ts": ts, "sha1": sha1}},
+            upsert=True,
+        )
+
     def content_add(
         self, cnts: Union[Iterable[Sha1Git], Dict[Sha1Git, Optional[datetime]]]
     ) -> bool:
-        data = cnts if isinstance(cnts, dict) else dict.fromkeys(cnts)
-        existing = {
-            x["sha1"]: x
-            for x in self.db.content.find(
-                {"sha1": {"$in": list(data)}}, {"sha1": 1, "ts": 1, "_id": 1}
-            )
-        }
-        for sha1, date in data.items():
-            ts = datetime.timestamp(date) if date is not None else None
-            if sha1 in existing:
-                cnt = existing[sha1]
-                if ts is not None and (cnt["ts"] is None or ts < cnt["ts"]):
-                    self.db.content.update_one(
-                        {"_id": cnt["_id"]}, {"$set": {"ts": ts}}
-                    )
-            else:
-                self.db.content.insert_one(
-                    {
-                        "sha1": sha1,
-                        "ts": ts,
-                        "revision": {},
-                        "directory": {},
-                    }
-                )
+        writes = [
+            self._generate_date_upserts(sha1, date)
+            for sha1, date in self._format_data(cnts).items()
+        ]
+        Entity.factory("content").bulk_write(self.db, writes)
+        return True
+
+    def directory_add(
+        self, dirs: Union[Iterable[Sha1Git], Dict[Sha1Git, Optional[datetime]]]
+    ) -> bool:
+        writes = [
+            self._generate_date_upserts(sha1, date)
+            for sha1, date in self._format_data(dirs).items()
+        ]
+        Entity.factory("directory").bulk_write(self.db, writes)
         return True
 
     def content_find_first(self, id: Sha1Git) -> Optional[ProvenanceResult]:
@@ -109,7 +114,11 @@
                     )
                 )
         for directory in self.db.directory.find(
-            {"_id": {"$in": [ObjectId(obj_id) for obj_id in content["directory"]]}}
+            {
+                "_id": {
+                    "$in": [ObjectId(obj_id) for obj_id in content.get("directory", {})]
+                }
+            }
         ):
             for revision in self.db.revision.find(
                 {"_id": {"$in": [ObjectId(obj_id) for obj_id in directory["revision"]]}}
@@ -148,28 +157,6 @@
             )
         }
 
-    def directory_add(
-        self, dirs: Union[Iterable[Sha1Git], Dict[Sha1Git, Optional[datetime]]]
-    ) -> bool:
-        data = dirs if isinstance(dirs, dict) else dict.fromkeys(dirs)
-        existing = {
-            x["sha1"]: x
-            for x in self.db.directory.find(
-                {"sha1": {"$in": list(data)}}, {"sha1": 1, "ts": 1, "_id": 1}
-            )
-        }
-        for sha1, date in data.items():
-            ts = datetime.timestamp(date) if date is not None else None
-            if sha1 in existing:
-                dir = existing[sha1]
-                if ts is not None and (dir["ts"] is None or ts < dir["ts"]):
-                    self.db.directory.update_one(
-                        {"_id": dir["_id"]}, {"$set": {"ts": ts}}
-                    )
-            else:
-                self.db.directory.insert_one({"sha1": sha1, "ts": ts, "revision": {}})
-        return True
-
     def directory_get(self, ids: Iterable[Sha1Git]) -> Dict[Sha1Git, datetime]:
         return {
             x["sha1"]: datetime.fromtimestamp(x["ts"], timezone.utc)
@@ -319,7 +306,7 @@
             if src_relation != "revision":
                 k = {
                     obj_id: list(set(paths + dsts.get(obj_id, [])))
-                    for obj_id, paths in src_objs[sha1][dst_relation].items()
+                    for obj_id, paths in src_objs[sha1].get(dst_relation, {}).items()
                 }
                 self.db.get_collection(src_relation).update_one(
                     {"_id": src_objs[sha1]["_id"]},
@@ -388,7 +375,7 @@
                 )
             }
             src_objs = {
-                x["sha1"]: x[dst]
+                x["sha1"]: x.get(dst, {})
                 for x in self.db.get_collection(src).find(
                     {}, {"_id": 0, "sha1": 1, dst: 1}
                 )
@@ -420,7 +407,7 @@
         src, *_, dst = relation.value.split("_")
         empty: Union[Dict[str, bytes], List[str]] = {} if src != "revision" else []
         src_objs = {
-            x["sha1"]: x[dst]
+            x["sha1"]: x.get(dst, {})
             for x in self.db.get_collection(src).find(
                 {dst: {"$ne": empty}}, {"_id": 0, "sha1": 1, dst: 1}
             )
diff --git a/swh/provenance/mongo/cache.py b/swh/provenance/mongo/cache.py
new file mode 100644
--- /dev/null
+++ b/swh/provenance/mongo/cache.py
@@ -0,0 +1,8 @@
+# Copyright (C) 2021  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
+
+
+class Cache:
+    pass
diff --git a/swh/provenance/mongo/data_model.json b/swh/provenance/mongo/data_model.json
new file mode 100644
--- /dev/null
+++ b/swh/provenance/mongo/data_model.json
@@ -0,0 +1,2 @@
+{
+}
diff --git a/swh/provenance/mongo/entity.py b/swh/provenance/mongo/entity.py
new file mode 100644
--- /dev/null
+++ b/swh/provenance/mongo/entity.py
@@ -0,0 +1,64 @@
+# Copyright (C) 2021  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 .errors import EntityError, DBError
+
+
+class Entity:
+    collection = ""
+    validate = True
+    data_model = {}
+
+    def __init__(self, data=None):
+        self.data = data
+
+    def save(self):
+        # validate the model if self.validate is true
+        # FIXME, set the obj in the cache
+        pass
+
+    def get(self, qry):
+        # FIXME, get from cache
+        pass
+
+    def bulk_write(self, db, writes):
+        if not writes:
+            return None
+        try:
+            result = db.get_collection(self.collection).bulk_write(writes)
+        except DBError as e:
+            # Log as mongo error
+            raise e
+        else:
+            return result
+
+    @staticmethod
+    def factory(entity):
+        mapping = {"content": Content, "directory": Directory}
+        if entity in mapping:
+            return mapping[entity]()
+        raise EntityError(f"invalid entity type {entity}")
+
+
+class Content(Entity):
+    collection = "content"
+    validate = False
+
+    @property
+    def revision(self):
+        return self.data.get("revision", {})
+
+    @property
+    def directory(self):
+        return self.data.get("directory", {})
+
+
+class Directory(Entity):
+    collection = "directory"
+    validate = False
+
+    @property
+    def revision(self):
+        return self.data.get("revision", {})
diff --git a/swh/provenance/mongo/errors.py b/swh/provenance/mongo/errors.py
new file mode 100644
--- /dev/null
+++ b/swh/provenance/mongo/errors.py
@@ -0,0 +1,13 @@
+# Copyright (C) 2021  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
+
+
+class DBError(Exception):
+    # FIXME, add mongo specific logging
+    pass
+
+
+class EntityError(Exception):
+    pass
diff --git a/swh/provenance/tests/mongo/test_backend.py b/swh/provenance/tests/mongo/test_backend.py
new file mode 100644
--- /dev/null
+++ b/swh/provenance/tests/mongo/test_backend.py
@@ -0,0 +1,236 @@
+# Copyright (C) 2021  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
+
+"""
+Unit tests for the mongo backend
+"""
+
+from datetime import datetime
+
+import pymongo.database
+import pytest
+
+from swh.provenance.mongo.backend import ProvenanceStorageMongoDb
+
+
+class TestBackend:
+    @pytest.fixture
+    def backend(self, mongodb: pymongo.database.Database):
+        return ProvenanceStorageMongoDb(mongodb)
+
+    # add content tests
+
+    def test_add_content_empty(self, backend, mongodb):
+        assert backend.content_add({}) is True
+        assert mongodb.content.count_documents({}) == 0
+
+        assert backend.content_add([]) is True
+        assert mongodb.content.count_documents({}) == 0
+
+    def test_add_content_with_insert(self, backend, mongodb):
+        # add data using add_contnet
+        # get data from mongo and compare
+        sha1 = "cf23df2207d99a74fbe169e3eba035e633b65d94"
+        data = {sha1: None}
+        assert backend.content_add(data) is True
+
+        assert mongodb.content.count_documents({}) == 1
+        cnt = mongodb.content.find_one({"sha1": sha1})
+        assert cnt["ts"] is None
+        assert cnt["revision"] == {}
+        assert cnt["directory"] == {}
+
+    def test_add_content_with_update_later_date(self, backend, mongodb):
+        sha1 = "cf23df2207d99a74fbe169e3eba035e633b65d94"
+        revision = {"test": "test"}
+        mongodb.content.insert_one(
+            {"sha1": sha1, "ts": 1631881748, "revision": revision, "directory": {}}
+        )
+
+        new_date = datetime(2010, 10, 10)
+        data = {sha1: new_date}
+        # data has a date before the one in the db
+        assert backend.content_add(data) is True
+        cnt = mongodb.content.find_one({"sha1": sha1})
+        assert cnt["ts"] == new_date.timestamp()
+        assert cnt["revision"] == revision
+        assert cnt["directory"] == {}
+
+    def test_add_content_with_update_none_date(self, backend, mongodb):
+        sha1 = "cf23df2207d99a74fbe169e3eba035e633b65d94"
+        revision = {"test": "test"}
+        mongodb.content.insert_one(
+            {"sha1": sha1, "ts": None, "revision": revision, "directory": {}}
+        )
+
+        new_date = datetime(2010, 10, 10)
+        data = {sha1: new_date}
+        # data has a date before the one in the db
+        assert backend.content_add(data) is True
+        cnt = mongodb.content.find_one({"sha1": sha1})
+        assert cnt["ts"] == new_date.timestamp()
+        assert cnt["revision"] == revision
+        assert cnt["directory"] == {}
+
+    def test_add_content_do_not_update_older_date(self, backend, mongodb):
+        sha1 = "cf23df2207d99a74fbe169e3eba035e633b65d94"
+        revision = {"test": "test"}
+        mongodb.content.insert_one(
+            {"sha1": sha1, "ts": 1286661600, "revision": revision, "directory": {}}
+        )
+
+        new_date = datetime(2020, 10, 10)
+        data = {sha1: new_date}
+        # data has a date after the one in the db
+        assert backend.content_add(data) is True
+        cnt = mongodb.content.find_one({"sha1": sha1})
+        assert cnt["ts"] == 1286661600
+
+    def test_add_content_multiple(self, backend, mongodb):
+        sha1_1 = "cf23df2207d99a74fbe169e3eba035e633b65d94"
+        sha1_2 = "a94a8fe5ccb19ba61c4c0873d391e987982fbbd3"
+        sha1_3 = "109f4b3c50d7b0df729d299bc6f8e9ef9066971f"
+        sha1_4 = "3ebfa301dc59196f18593c45e519287a23297589"
+        revision = {"test": "test"}
+        mongodb.content.insert_one(
+            {"sha1": sha1_1, "ts": 1286661600, "revision": revision, "directory": {}}
+        )
+        mongodb.content.insert_one(
+            {"sha1": sha1_2, "ts": None, "revision": revision, "directory": {}}
+        )
+        mongodb.content.insert_one(
+            {"sha1": sha1_3, "ts": 1631889655, "revision": revision, "directory": {}}
+        )
+
+        data = {
+            sha1_1: datetime(2020, 10, 10),  # given date is in future, no update
+            sha1_2: datetime(2020, 10, 10),  # will update None date
+            sha1_3: datetime(2010, 10, 10),  # date in the past, will update
+            sha1_4: datetime(2010, 10, 10),  # new rcd, will insert
+        }
+
+        assert backend.content_add(data) is True
+        mongodb.content.count_documents({}) == 4
+        cnt = mongodb.content.find_one({"sha1": sha1_1})
+        assert cnt["ts"] == 1286661600
+        assert cnt["revision"] == revision
+        assert cnt["directory"] == {}
+
+        cnt = mongodb.content.find_one({"sha1": sha1_2})
+        assert cnt["ts"] == datetime(2020, 10, 10).timestamp()
+        assert cnt["revision"] == revision
+        assert cnt["directory"] == {}
+
+        cnt = mongodb.content.find_one({"sha1": sha1_3})
+        assert cnt["ts"] == datetime(2010, 10, 10).timestamp()
+        assert cnt["revision"] == revision
+        assert cnt["directory"] == {}
+
+        cnt = mongodb.content.find_one({"sha1": sha1_4})
+        assert cnt["ts"] == datetime(2010, 10, 10).timestamp()
+        assert cnt["revision"] == {}
+        assert cnt["directory"] == {}
+
+    # add directory tests
+
+    def test_add_directory_empty(self, backend, mongodb):
+        assert backend.directory_add({}) is True
+        assert mongodb.directory.count_documents({}) == 0
+
+        assert backend.directory_add([]) is True
+        assert mongodb.directory.count_documents({}) == 0
+
+    def test_add_directory_with_insert(self, backend, mongodb):
+        # add data using add_contnet
+        # get data from mongo and compare
+        sha1 = "cf23df2207d99a74fbe169e3eba035e633b65d94"
+        data = {sha1: None}
+        assert backend.directory_add(data) is True
+
+        assert mongodb.directory.count_documents({}) == 1
+        cnt = mongodb.directory.find_one({"sha1": sha1})
+        assert cnt["ts"] is None
+        assert cnt["revision"] == {}
+
+    def test_add_directory_with_update_later_date(self, backend, mongodb):
+        sha1 = "cf23df2207d99a74fbe169e3eba035e633b65d94"
+        revision = {"test": "test"}
+        mongodb.directory.insert_one(
+            {"sha1": sha1, "ts": 1631881748, "revision": revision}
+        )
+
+        new_date = datetime(2010, 10, 10)
+        data = {sha1: new_date}
+        # data has a date before the one in the db
+        assert backend.directory_add(data) is True
+        diy = mongodb.directory.find_one({"sha1": sha1})
+        assert diy["ts"] == new_date.timestamp()
+        assert diy["revision"] == revision
+
+    def test_add_directory_with_update_none_date(self, backend, mongodb):
+        sha1 = "cf23df2207d99a74fbe169e3eba035e633b65d94"
+        revision = {"test": "test"}
+        mongodb.directory.insert_one({"sha1": sha1, "ts": None, "revision": revision})
+
+        new_date = datetime(2010, 10, 10)
+        data = {sha1: new_date}
+        # data has a date before the one in the db
+        assert backend.directory_add(data) is True
+        diy = mongodb.directory.find_one({"sha1": sha1})
+        assert diy["ts"] == new_date.timestamp()
+        assert diy["revision"] == revision
+
+    def test_add_directory_do_not_update_older_date(self, backend, mongodb):
+        sha1 = "cf23df2207d99a74fbe169e3eba035e633b65d94"
+        revision = {"test": "test"}
+        mongodb.directory.insert_one(
+            {"sha1": sha1, "ts": 1286661600, "revision": revision}
+        )
+
+        new_date = datetime(2020, 10, 10)
+        data = {sha1: new_date}
+        # data has a date after the one in the db
+        assert backend.directory_add(data) is True
+        cnt = mongodb.directory.find_one({"sha1": sha1})
+        assert cnt["ts"] == 1286661600
+
+    def test_add_directory_multiple(self, backend, mongodb):
+        sha1_1 = "cf23df2207d99a74fbe169e3eba035e633b65d94"
+        sha1_2 = "a94a8fe5ccb19ba61c4c0873d391e987982fbbd3"
+        sha1_3 = "109f4b3c50d7b0df729d299bc6f8e9ef9066971f"
+        sha1_4 = "3ebfa301dc59196f18593c45e519287a23297589"
+        revision = {"test": "test"}
+        mongodb.directory.insert_one(
+            {"sha1": sha1_1, "ts": 1286661600, "revision": revision}
+        )
+        mongodb.directory.insert_one({"sha1": sha1_2, "ts": None, "revision": revision})
+        mongodb.directory.insert_one(
+            {"sha1": sha1_3, "ts": 1631889655, "revision": revision}
+        )
+
+        data = {
+            sha1_1: datetime(2020, 10, 10),  # given date is in future, no update
+            sha1_2: datetime(2020, 10, 10),  # will update None date
+            sha1_3: datetime(2010, 10, 10),  # date in the past, will update
+            sha1_4: datetime(2010, 10, 10),  # new rcd, will insert
+        }
+
+        assert backend.directory_add(data) is True
+        mongodb.directory.count_documents({}) == 4
+        dry = mongodb.directory.find_one({"sha1": sha1_1})
+        assert dry["ts"] == 1286661600
+        assert dry["revision"] == revision
+
+        dry = mongodb.directory.find_one({"sha1": sha1_2})
+        assert dry["ts"] == datetime(2020, 10, 10).timestamp()
+        assert dry["revision"] == revision
+
+        dry = mongodb.directory.find_one({"sha1": sha1_3})
+        assert dry["ts"] == datetime(2010, 10, 10).timestamp()
+        assert dry["revision"] == revision
+
+        dry = mongodb.directory.find_one({"sha1": sha1_4})
+        assert dry["ts"] == datetime(2010, 10, 10).timestamp()
+        assert dry["revision"] == {}