API Design · Senior · Question 11 of 75

How should idempotency keys behave when the first request is still in progress and a retry arrives?

✓Correct answer: The retry should wait or get a 409/'in progress' response, not start the work a second time; a lock on the key prevents concurrent execution
2The second request should cancel the first
3Both requests should run

Explanation

Store the key before doing work, with a status. Release or expire locks if the worker crashes.

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