diff --git a/swh/storage/vault/cache.py b/swh/storage/vault/cache.py
--- a/swh/storage/vault/cache.py
+++ b/swh/storage/vault/cache.py
@@ -31,6 +31,14 @@
         storage = self._get_storage(obj_type)
         return storage.get(hashutil.hash_to_bytes(obj_id))
 
+    def add_stream(self, obj_type, obj_id, content_iter):
+        storage = self._get_storage(obj_type)
+        return storage.add_stream(content_iter, obj_id)
+
+    def get_stream(self, obj_type, obj_id):
+        storage = self._get_storage(obj_type)
+        return storage.get_stream(hashutil.hash_to_bytes(obj_id))
+
     def is_cached(self, obj_type, obj_id):
         storage = self._get_storage(obj_type)
         return hashutil.hash_to_bytes(obj_id) in storage
diff --git a/swh/storage/vault/cookers/base.py b/swh/storage/vault/cookers/base.py
--- a/swh/storage/vault/cookers/base.py
+++ b/swh/storage/vault/cookers/base.py
@@ -65,7 +65,7 @@
 
     @abc.abstractmethod
     def prepare_bundle(self):
-        """Implementation of the cooker. Returns the bundle bytes.
+        """Implementation of the cooker. Yields chunks of the bundle bytes.
 
         Override this with the cooker implementation.
         """
@@ -74,20 +74,20 @@
     def cook(self):
         """Cook the requested object into a bundle
         """
-        bundle_content = self.prepare_bundle()
+        content_iter = self.prepare_bundle()
 
         # Cache the bundle
-        self.update_cache(bundle_content)
+        self.update_cache(content_iter)
         # Make a notification that the bundle have been cooked
         # NOT YET IMPLEMENTED see TODO in function.
         self.notify_bundle_ready(
             notif_data='Bundle %s ready' % hashutil.hash_to_hex(self.obj_id))
 
-    def update_cache(self, bundle_content):
+    def update_cache(self, content_iter):
         """Update the cache with id and bundle_content.
 
         """
-        self.cache.add(self.CACHE_TYPE_KEY, self.obj_id, bundle_content)
+        self.cache.add_stream(self.CACHE_TYPE_KEY, self.obj_id, content_iter)
 
     def notify_bundle_ready(self, notif_data):
         # TODO plug this method with the notification method once
diff --git a/swh/storage/vault/cookers/directory.py b/swh/storage/vault/cookers/directory.py
--- a/swh/storage/vault/cookers/directory.py
+++ b/swh/storage/vault/cookers/directory.py
@@ -21,4 +21,4 @@
 
         """
         directory_builder = DirectoryBuilder(self.storage)
-        return directory_builder.get_directory_bytes(self.obj_id)
+        yield directory_builder.get_directory_bytes(self.obj_id)
diff --git a/swh/storage/vault/cookers/revision_flat.py b/swh/storage/vault/cookers/revision_flat.py
--- a/swh/storage/vault/cookers/revision_flat.py
+++ b/swh/storage/vault/cookers/revision_flat.py
@@ -30,4 +30,5 @@
                 revdir.mkdir()
                 directory_builder.build_directory(revision['directory'],
                                                   str(revdir).encode())
-            return get_tar_bytes(root_tmp, hashutil.hash_to_hex(self.obj_id))
+            # FIXME: stream the bytes! this tarball can be HUUUUUGE
+            yield get_tar_bytes(root_tmp, hashutil.hash_to_hex(self.obj_id))
diff --git a/swh/storage/vault/cookers/revision_git.py b/swh/storage/vault/cookers/revision_git.py
--- a/swh/storage/vault/cookers/revision_git.py
+++ b/swh/storage/vault/cookers/revision_git.py
@@ -17,9 +17,11 @@
     CACHE_TYPE_KEY = 'revision_git'
 
     def prepare_bundle(self):
-        commands = self.fastexport(self.storage.revision_log([self.obj_id]))
-        bundle_content = b'\n'.join(bytes(command) for command in commands)
-        return bundle_content
+        log = self.storage.revision_log([self.obj_id])
+        commands = self.fastexport(log)
+
+        for command in commands:
+            yield bytes(command)
 
     def fastexport(self, log):
         """Generate all the git fast-import commands from a given log.