One Time Access URL after purchasing subscription

A simple solution would be creating a unique token upon purchasing a subscription/product.

  1. Save to token somewhere in database.

  2. Present the URL to the app passing the token as a GET variable. For eample, www.company.com/app/the-awesome-tool/?token=jvp2HBst5V7iHQeE2twq

  3. When accessed, check is the token is there at the database, if not restrict access.

  4. Delete the token from database if the access was granted.

This could be extended by comparing user ID, order id etc.