Using cache validation means that the request will make a network call and hit the application, regardless. The application must take care of the ETag and decide if the former response is still valid or not. This, effectively, means that your application will build the whole response again just to calculate the ETag. This means that ETags will save you some bandwidth if your responses are heavy, but may not save you too much otherwise. If your responses are heavy, usually the first response is to gzip.