diff --git a/keystone/assignment/backends/kvs.py b/keystone/assignment/backends/kvs.py
index bbcf9e3343..27614b37e3 100644
--- a/keystone/assignment/backends/kvs.py
+++ b/keystone/assignment/backends/kvs.py
@@ -58,8 +58,7 @@ class Assignment(kvs.Base, assignment.Driver):
             raise exception.ProjectNotFound(project_id=tenant_id)
 
     def _build_project_refs(self):
-        project_keys = filter(lambda x: x.startswith("tenant-"),
-                              self.db.keys())
+        project_keys = (k for k in self.db.keys() if k.startswith('tenant-'))
         return [self.db.get(key) for key in project_keys]
 
     def list_projects(self, hints):
@@ -68,9 +67,7 @@ class Assignment(kvs.Base, assignment.Driver):
     def list_projects_in_domain(self, domain_id):
         project_refs = self._build_project_refs()
         self.get_domain(domain_id)
-        project_refs = filter(lambda x: domain_id in x['domain_id'],
-                              project_refs)
-        return project_refs
+        return [ref for ref in project_refs if domain_id in ref['domain_id']]
 
     def get_project_by_name(self, tenant_name, domain_id):
         try:
@@ -83,8 +80,8 @@ class Assignment(kvs.Base, assignment.Driver):
 
         user_ids = set()
 
-        metadata_keys = filter(lambda x: x.startswith("metadata_user-"),
-                               self.db.keys())
+        metadata_keys = (k for k in self.db.keys()
+                         if k.startswith('metadata_user-'))
         for key in metadata_keys:
             i, meta_project_or_domain_id, meta_user_id = key.split('-')
 
@@ -136,8 +133,8 @@ class Assignment(kvs.Base, assignment.Driver):
 
         project_ids = set()
 
-        metadata_keys = filter(lambda x: x.startswith('metadata_user-'),
-                               self.db.keys())
+        metadata_keys = (k for k in self.db.keys()
+                         if k.startswith('metadata_user-'))
         for key in metadata_keys:
             i, meta_project_or_domain_id, meta_user_id = key.split('-')
 
@@ -216,8 +213,8 @@ class Assignment(kvs.Base, assignment.Driver):
 
         """
         assignment_list = []
-        metadata_keys = filter(lambda x: x.startswith('metadata_user-'),
-                               self.db.keys())
+        metadata_keys = (k for k in self.db.keys()
+                         if k.startswith('metadata_user-'))
         for key in metadata_keys:
             template = {}
             i, meta_project_or_domain_id, template['user_id'] = key.split('-')
@@ -235,8 +232,8 @@ class Assignment(kvs.Base, assignment.Driver):
                 role_assignment['role_id'] = r
                 assignment_list.append(role_assignment)
 
-        metadata_keys = filter(lambda x: x.startswith('metadata_group-'),
-                               self.db.keys())
+        metadata_keys = (k for k in self.db.keys()
+                         if k.startswith('metadata_group-'))
         for key in metadata_keys:
             template = {}
             i, meta_project_or_domain_id, template['group_id'] = key.split('-')
@@ -372,8 +369,8 @@ class Assignment(kvs.Base, assignment.Driver):
     def delete_role(self, role_id):
         self.get_role(role_id)
 
-        metadata_keys = filter(lambda x: x.startswith('metadata_user-'),
-                               self.db.keys())
+        metadata_keys = (k for k in self.db.keys()
+                         if k.startswith('metadata_user-'))
         for key in metadata_keys:
             i, meta_project_or_domain_id, meta_user_id = key.split('-')
             try:
@@ -388,8 +385,8 @@ class Assignment(kvs.Base, assignment.Driver):
             except exception.NotFound:
                 pass
 
-        metadata_keys = filter(lambda x: x.startswith('metadata_group-'),
-                               self.db.keys())
+        metadata_keys = (k for k in self.db.keys()
+                         if k.startswith('metadata_group-'))
         for key in metadata_keys:
             i, meta_project_or_domain_id, meta_group_id = key.split('-')
             try:
diff --git a/keystone/identity/backends/kvs.py b/keystone/identity/backends/kvs.py
index 27a107f24a..4892dd9a5d 100644
--- a/keystone/identity/backends/kvs.py
+++ b/keystone/identity/backends/kvs.py
@@ -189,10 +189,10 @@ class Identity(kvs.Base, identity.Driver):
 
     def list_users_in_group(self, group_id, hints):
         self.get_group(group_id)
-        user_keys = filter(lambda x: x.startswith("user-"), self.db.keys())
-        user_refs = [self.db.get(key) for key in user_keys]
-        user_refs_for_group = filter(lambda x: group_id in x['groups'],
-                                     user_refs)
+        user_keys = (k for k in self.db.keys() if k.startswith('user-'))
+        user_refs = (self.db.get(key) for key in user_keys)
+        user_refs_for_group = (ref for ref in user_refs
+                               if group_id in ref['groups'])
         return [identity.filter_user(x) for x in user_refs_for_group]
 
     def list_groups_for_user(self, user_id, hints):
@@ -277,8 +277,8 @@ class Identity(kvs.Base, identity.Driver):
         except exception.NotFound:
             raise exception.GroupNotFound(group_id=group_id)
         # Delete any entries in the group lists of all users
-        user_keys = filter(lambda x: x.startswith("user-"), self.db.keys())
-        user_refs = [self.db.get(key) for key in user_keys]
+        user_keys = (k for k in self.db.keys() if k.startswith('user-'))
+        user_refs = (self.db.get(key) for key in user_keys)
         for user_ref in user_refs:
             groups = set(user_ref.get('groups', []))
             if group_id in groups:
diff --git a/keystone/notifications.py b/keystone/notifications.py
index 30c0815e79..a7977e796c 100644
--- a/keystone/notifications.py
+++ b/keystone/notifications.py
@@ -137,8 +137,7 @@ def register_event_callback(event, resource_type, callbacks):
             msg = _('Callback: `%(callback)s` subscribed to event '
                     '`%(event)s`.')
             callback_info = _get_callback_info(callback)
-            callback_str = '.'.join(
-                filter(lambda i: i is not None, callback_info))
+            callback_str = '.'.join(i for i in callback_info if i is not None)
             event_str = '.'.join(['identity', resource_type, event])
             LOG.info(msg, {'callback': callback_str, 'event': event_str})