diff --git a/swh/storage/in_memory.py b/swh/storage/in_memory.py
--- a/swh/storage/in_memory.py
+++ b/swh/storage/in_memory.py
@@ -38,6 +38,7 @@
         self._snapshots = {}
         self._origins = []
         self._origin_visits = []
+        self._persons = []
         self._origin_metadata = defaultdict(list)
         self._tools = {}
         self._metadata_providers = {}
@@ -415,6 +416,8 @@
         for revision in revisions:
             if revision['id'] not in self._revisions:
                 self._revisions[revision['id']] = rev = copy.deepcopy(revision)
+                self._person_add(rev['committer'])
+                self._person_add(rev['author'])
                 rev['date'] = normalize_timestamp(rev.get('date'))
                 rev['committer_date'] = normalize_timestamp(
                         rev.get('committer_date'))
@@ -499,10 +502,12 @@
         the date dictionary has the form defined in :mod:`swh.model`.
         """
         for rel in releases:
+            rel = copy.deepcopy(rel)
             rel['date'] = normalize_timestamp(rel['date'])
+            self._person_add(rel['author'])
             self._objects[rel['id']].append(
                 ('release', rel['id']))
-        self._releases.update((rel['id'], rel) for rel in releases)
+            self._releases[rel['id']] = rel
 
     def release_missing(self, releases):
         """List releases missing from storage
@@ -1016,6 +1021,46 @@
             origin_visit = self._origin_visits[origin-1][visit-1]
         return origin_visit
 
+    def _person_add(self, person):
+        """Add a person in storage.
+
+        Note: Internal function for now, do not use outside of this module.
+
+        Do not do anything fancy in case a person already exists.
+        Please adapt code if more checks are needed.
+
+        Args:
+            person: dictionary with keys name and email.
+
+        Returns:
+            Id of the new person.
+
+        """
+        if person not in self._persons:
+            person_id = len(self._persons) + 1
+            self._persons.append(dict(person))
+            key = (person['name'], person['email'])
+            self._objects[key].append(('person', person_id))
+        else:
+            person_id = self._persons.index(person)
+            person_id = person_id + 1
+        person['id'] = person_id
+        return person_id
+
+    def person_get(self, person):
+        """Return the persons identified by their ids.
+
+        Args:
+            person: array of ids.
+
+        Returns:
+            The array of persons corresponding of the ids.
+
+        """
+        for p in person:
+            yield dict(self._persons[p - 1], id=p) \
+                if 0 <= (p - 1) < len(self._persons) else None
+
     def stat_counters(self):
         """compute statistics about the number of tuples in various tables
 
diff --git a/swh/storage/tests/test_api_client.py b/swh/storage/tests/test_api_client.py
--- a/swh/storage/tests/test_api_client.py
+++ b/swh/storage/tests/test_api_client.py
@@ -62,6 +62,10 @@
     def test_stat_counters(self):
         pass
 
+    @pytest.mark.skip('The remote API does not expose _person_add.')
+    def test_person_get(self):
+        pass
+
 
 @pytest.mark.db
 @pytest.mark.property_based
diff --git a/swh/storage/tests/test_storage.py b/swh/storage/tests/test_storage.py
--- a/swh/storage/tests/test_storage.py
+++ b/swh/storage/tests/test_storage.py
@@ -1205,6 +1205,42 @@
 
         self.assertIsNone(actual_origin_visit)
 
+    def test_person_get(self):
+        # given
+        person0 = {
+            'fullname': b'bob <alice@bob>',
+            'name': b'bob',
+            'email': b'alice@bob',
+        }
+        id0 = self.storage._person_add(person0)
+
+        person1 = {
+            'fullname': b'tony <tony@bob>',
+            'name': b'tony',
+            'email': b'tony@bob',
+        }
+        id1 = self.storage._person_add(person1)
+
+        # when
+        actual_persons = self.storage.person_get([id0, id1])
+
+        # given (person injection through release for example)
+        self.assertEqual(
+            list(actual_persons), [
+                {
+                    'id': id0,
+                    'fullname': person0['fullname'],
+                    'name': person0['name'],
+                    'email': person0['email'],
+                },
+                {
+                    'id': id1,
+                    'fullname': person1['fullname'],
+                    'name': person1['name'],
+                    'email': person1['email'],
+                },
+            ])
+
     def test_snapshot_add_get_empty(self):
         origin_id = self.storage.origin_add_one(self.origin)
         origin_visit1 = self.storage.origin_visit_add(origin_id,
@@ -1507,6 +1543,7 @@
         self.assertEqual(counters['snapshot'], 1)
         self.assertEqual(counters['origin'], 1)
         self.assertEqual(counters['revision'], 1)
+        self.assertEqual(counters['person'], 2)
 
     def test_content_find_with_present_content(self):
         # 1. with something to find
@@ -2104,43 +2141,6 @@
 
         self.assertEqual(expected_fetch_history, fetch_history)
 
-    # The remote API doesn't expose _person_add
-    def test_person_get(self):
-        # given
-        person0 = {
-            'fullname': b'bob <alice@bob>',
-            'name': b'bob',
-            'email': b'alice@bob',
-        }
-        id0 = self.storage._person_add(person0)
-
-        person1 = {
-            'fullname': b'tony <tony@bob>',
-            'name': b'tony',
-            'email': b'tony@bob',
-        }
-        id1 = self.storage._person_add(person1)
-
-        # when
-        actual_persons = self.storage.person_get([id0, id1])
-
-        # given (person injection through release for example)
-        self.assertEqual(
-            list(actual_persons), [
-                {
-                    'id': id0,
-                    'fullname': person0['fullname'],
-                    'name': person0['name'],
-                    'email': person0['email'],
-                },
-                {
-                    'id': id1,
-                    'fullname': person1['fullname'],
-                    'name': person1['name'],
-                    'email': person1['email'],
-                },
-            ])
-
     # This test is only relevant on the local storage, with an actual
     # objstorage raising an exception
     def test_content_add_objstorage_exception(self):