How should I implement friend's data loading?

Question

I'm writing an Android app using the phone number as the ID. I am getting all the contacts from the client's phone. I want to display to the user all of his contacts whom installed the app (just like whatsapp).

I was thinking about sending to the server all of the contacts and execute a search for each one of them to check if they exist in the db, and send back all the registered players. I am afraid this implementation will slow my app since I have to load all of his friends on every loading page (in case of new contacts that installed the app, or deleted and so on)

What are your thoughts about it?

Answer 1

Use a contacts cache and invalidate/recreate it whenever the contacts DB change, use code such as how to listen for changes in Contact Database. That should make your suggested approach fast enough.

Cheers.