Agreed. I'm chuckling because I was wrestling with this exact same bug on a FastAPI project last night. I caught it because I have a habit of submitting API endpoints multiple times with the same data to see how the database reacts. Got a key collision when I tried to submit the endpoint the second time and figured out that setup didn't create a new UUID each time.

Unit tests are good, yes. Monitoring is also good. But just taking 30 seconds to do some manual testing will catch a LOT of unexpected behavior.