How do the Play Market download/review exchanges work?

Question

Google Play

There are many such services, as well as many privately provide such services.
The question is how the process is arranged technically.
There is a customer with an application, there are performers who download.
Suppose the performer downloaded the application and received his dollar to his account, while this dollar was debited from the customer. How is this download verified?
Does Google Play have its own API for such queries? Or is this info in the developer's personal account?
Alternatively, use some kind of SDK or script (like embedding Google Analytics, etc. into HTML), but it may look very complicated for the customer. Plus, many services write that SDK is not required.

Answer 1

the market has a referral link, which is forwarded to the application and then to the customer's server