Using push notification for purchase authorization.
For example, if a customer rents a movie on our app, we need to know on our backend that they have purchased it so the backend authorizes access.
Push notifications are great for providing notifications on transactions occurring in your channel, but for access authorization, we'd recommend using validateTransaction.
When a user buys an in-channel product, the app should pass the transactionID to your backend. Then, your backend calls validateTransaction to determine authorization via the isEntitled field. You can read more about this process on this developer doc article.