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Three facts about how events flow that save a lot of debugging.

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Duplicates: design for at-least-once

A provider that doesn’t get a fast success from you will resend — so the same logical event can arrive more than once. Two tools:
  • Deduplication. Turn on a dedup mode for an endpoint and webhook.co collapses repeats into the event you already have (and dedup-collapsed duplicates never count as usage).
  • Idempotency in your receiver. Log each event’s id and, if you see one you’ve already processed, return 200 and stop — acknowledging a duplicate you discard is correct and keeps the sender from retrying.

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Ordering isn’t guaranteed

Events are delivered at least once, not strictly in order. Don’t rely on receiving events in the exact sequence they occurred — use timestamps or sequence numbers in the payload if order matters to your logic.

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Retries: a receiver blip is never your loss

Outbound deliveries retry automatically on a fixed schedule (up to 8 attempts over ~32h) before dead-lettering, and inbound capture is durable before anything else runs. A brief outage on either side doesn’t drop events — see delivery failures.

Deduplication

Configure how repeats are collapsed.

An idempotent consumer

A worked example.