Quotas and Usage Limits

A usage allowance is only useful if the service can enforce it while requests overlap. Suppose a bookstore has one export left in its monthly allowance, and two administrators start exports at the same time. Both requests read the same remaining balance, both proceed, and the service produces two exports. The dashboard eventually reports that the exports exceeded the allowance, but the work has already happened.

Quotas turn a usage policy into an enforceable resource boundary.

This chapter explains what to count, when to reserve and consume allowance, how to handle retries and incomplete work, and how to expose limits clearly. The examples use a fictional bookstore API over HTTPS at api.bookstore.example.