Index: swh/indexer/indexer.py
===================================================================
--- swh/indexer/indexer.py
+++ swh/indexer/indexer.py
@@ -18,6 +18,7 @@
 from swh.objstorage.exc import ObjNotFoundError
 from swh.indexer.storage import get_indexer_storage, INDEXER_CFG_KEY
 from swh.model import hashutil
+from swh.core import utils
 
 
 class DiskIndexer:
@@ -396,6 +397,9 @@
             **end** (bytes): End range identifier
             **indexed** (Set[bytes]): Set of content already indexed.
 
+        Yields:
+            Identifier (bytes) of contents to index.
+
         """
         while start:
             result = self.storage.content_get_range(start, end)
@@ -407,6 +411,29 @@
                 yield _id
             start = result['next']
 
+    def index_contents(self, start, end, indexed, **kwargs):
+        """Index the contents from within range [start, end]
+
+        Args:
+            **start** (bytes): Starting bound from range identifier
+            **end** (bytes): End range identifier
+            **indexed** (Set[bytes]): Set of content already indexed.
+
+        Yields:
+            Data indexed (dict) to persist using the indexer storage
+
+        """
+        for sha1 in self.list_contents_to_index(start, end, indexed):
+            try:
+                raw_content = self.objstorage.get(sha1)
+            except ObjNotFoundError:
+                self.log.warning('Content %s not found in objstorage' %
+                                 hashutil.hash_to_hex(sha1))
+                continue
+            res = self.index(sha1, raw_content, **kwargs)
+            if res:
+                yield res
+
     def run(self, ids, policy_update, **kwargs):
         """Given a range of content ids, compute the indexing computation on
            the contents within. Either only new ones (policy_update to
@@ -420,10 +447,14 @@
                                      only compute new ones
             **kwargs: passed to the `index` method
 
+        Returns:
+            None if no data was indexed, a partial result otherwise (dict).
+            Partial because the result is not really used later.
+
         """
         if len(ids) != 2:  # range
             raise ValueError('Range of ids expected')
-        results = []
+        results = None
         try:
             [start, end] = ids
             if isinstance(start, str):
@@ -436,19 +467,11 @@
             else:
                 indexed = set()
 
-            for sha1 in self.list_contents_to_index(start, end, indexed):
-                try:
-                    raw_content = self.objstorage.get(sha1)
-                except ObjNotFoundError:
-                    self.log.warning('Content %s not found in objstorage' %
-                                     hashutil.hash_to_hex(sha1))
-                    continue
-                res = self.index(sha1, raw_content, **kwargs)
-                if res:  # If no results, skip it
-                    results.append(res)
-
-            self.persist_index_computations(results, policy_update)
-            return results
+            index_computations = self.index_contents(start, end, indexed)
+            for results in utils.grouper(index_computations,
+                                         n=self.config['batch_write']):
+                self.persist_index_computations(results, policy_update)
+            return results  # return a partial result if any
         except Exception:
             self.log.exception(
                 'Problem when computing metadata.')
Index: swh/indexer/mimetype.py
===================================================================
--- swh/indexer/mimetype.py
+++ swh/indexer/mimetype.py
@@ -37,12 +37,12 @@
 
     """
     ADDITIONAL_CONFIG = {
-        'scheduler': {
+        'scheduler': ('dict', {
             'cls': 'remote',
             'args': {
                 'url': 'http://localhost:5008',
             },
-        },
+        }),
         'tools': ('dict', {
             'name': 'file',
             'version': '1:5.30-1+deb9u1',
@@ -51,6 +51,7 @@
                 "debian-package": "python3-magic"
             },
         }),
+        'batch_write': ('int', 100),
     }
 
     CONFIG_BASE_FILENAME = 'indexer/mimetype'
Index: swh/indexer/tests/test_mimetype.py
===================================================================
--- swh/indexer/tests/test_mimetype.py
+++ swh/indexer/tests/test_mimetype.py
@@ -234,6 +234,7 @@
                     "debian-package": "python3-magic"
                 },
             },
+            'batch_write': 100,
         }
         self.idx_storage = _MockIndexerStorage()
         self.log = logging.getLogger('swh.indexer')