NestJS · Senior · Question 49 of 75

How can one interceptor implement idempotency keys for POST endpoints?

1Return 409 for every repeated POST
✓Correct answer: Read the Idempotency-Key header, return a stored response if the key was seen, otherwise lock the key, call next.handle() and store the result
3Interceptors can't access headers

Explanation

Store keys in Redis or the database with the request hash; handle concurrent requests with the same key via a lock.

Further reading

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