What is the correct approach to validate new data by an Android app?

Question

Android

Good day gentlemen, I'm already tired of looking for the right answer.
The task is to check for changes in an external database on the
Android Internet using an application using the API on the Apache server, of course.
Which method in the application itself should be used in your opinion?
I will clarify right away, the check interval is minimal.
I will make a reservation that, in fact, you need to somehow implement the listener, if you can call it that, but only the external one.
Everything will work in Service. This is clear to me.
Please don't deploy the GCM topic.
I look forward to your advice.

Answer 1

The first thing that comes to mind is that the data in the database has changed on the server, the timestamp has been written down.
The application receives data with a timestamp, makes an update request with the latest data timestamp, the server checks and gives or does not give data.