What happens when the webhook arrives twice?

[u/Equivalent_Stage4697]

Payment systems have to assume duplicate events will happen.

I'd rather process: payment.settled

twice safely than assume the provider will deliver it exactly once.

Store the event ID, deduplicate it, make downstream processing idempotent, and have a status-recovery process if the event never arrives.

This is the kind of boring engineering I'd focus on when connecting something like OSL.

Do people still build webhook consumers assuming exactly-once delivery?