Glossary
Fan-Out
Delivering a single source event to multiple downstream consumers — one 'order.created' triggering fulfillment, analytics, and email independently.
Fan-out is the pattern where one event needs to reach several independent consumers. A single order.created might need to hit your fulfillment service, your analytics pipeline, and a customer-email worker — each owned by a different team, each able to fail or retry on its own schedule.
Doing this from one webhook handler couples everything: if the email step throws, you can't easily avoid re-running fulfillment. The clean approach is to receive the webhook once, publish it to a message bus (SNS, Kafka, EventBridge) or an event gateway, and let each consumer subscribe independently with its own retries and DLQ.
Fan-out is a *delivery* concern, not a *debugging* one — but you still need to inspect what the upstream provider actually sent before you can route it correctly.
How HookSense helps
HookSense is the inspection layer in front of a fan-out architecture: capture and verify the source event, then pair with a gateway like Hookdeck or Svix to do the multi-consumer delivery.
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