Comment by piaste

> You can't have idempotency without determinism

You absolutely can. The idempotency nonce must be generated by the client who is responsible for firing potential retries. And a random UUIDv4 is a perfectly fine nonce.

If the client _doesn't_ generate a nonce, it doesn't matter what the server side does, they cannot tell from the request data if it's supposed to be a retry or a new request with the same data. A hash such as a UUIDv5 is more performant but not logically any better than comparing the raw data of the two requests. If you use that UUIDv5 as your primary key for insert/update, it's little more than a natural key, with all its well-known drawbacks.