How to organize the architecture of a SaaS application with free and paid access packages?

Question

Software design

Good day.
Often, many services provide different plans for working with them, differing, for example, in the number of requests to the service. For example, a free plan with a limit of 100 requests per month, there are some paid plans, let's call them Plan 1000 (1000 requests), Plan 10000 (10000 requests).
What is the best way to organize the architecture in such applications?
So far, the following plan of action came to mind:
After registration, the user receives a unique code, this code is also entered in a table where the allowable number of requests for this key is indicated. On each call to api with this key, reduce the value of requests, and as soon as it reaches 0, notify the user.
Maybe there are some more correct ways to build such services.
How the automatic calculation of consumed resources works for each plan.

Answer 1

As you come up with it, it will be the way you described the solution to yourself.