gistfile1.py

class CleanupHandler(webapp.RequestHandler):
    def get(self):
        posts = Post.all().filter('created <', datetime.datetime.now() - datetime.timedelta(days=90))
        assert posts.count()
        try:
            while True:
                db.delete(posts.fetch(500))
                time.sleep(0.1)
        except DeadlineExceededError:
            self.response.clear()
            self.response.set_status(200)