It is important to limit and optimise network traffic in mobile communications.
A well designed rest client is the best you can do in order to save network bandwidth and increase your online app responsiveness.
This talk is focused on how to create an optimal rest client with persistent cache in Android using HTTP/2, Retrofit, OkHttp and Realm while relying on an AppEngine hosted backend.
Link: http://it.droidcon.com/2016/sessions/build-an-efficient-rest-client-on-android/