How to make requests to the VK API correctly and not duplicate information?

Question

API

How to make requests to the VK API correctly and, when you receive data, do not duplicate them, but check whether this is already in my application or not?
I want to make a bot for Telegram that will parse posts from VK through its API. But I don't understand how to make it so that there are no duplicates.
How to get data only when it is updated?
Like, for example, I have a new post on the wall and that's just to pick it up.
How is this done, for example, in the same VK clients for iOS and Android?
How to do this at all?

Answer 1

VK Callback API you need. Subscribe to events and your application receives data only when events occur.