Raw research, debugging sessions, and technical findings. Atomic notes from real work.
16 notes · Page 3 of 6
Calling a customer's URL sounds trivial. It's really four problems: who may subscribe, proving the call came from you, surviving their outage, and not slowing down the request that triggered it.
A POST that timed out leaves the caller with nothing safe to do. An Idempotency-Key header, backed by a key derived into the data and a database that rejects duplicates, makes the retry safe.
Save the record, then publish the event, and a crash in between means nobody hears about it. The outbox pattern closes the gap, and the price is at-least-once delivery your handlers have to survive.
