FanOut

One input triggers multiple independent, parallel outputs/consumers — e.g. one event dispatched to several downstream handlers.

Why we need this / what value this brings

Lets independent consumers react to the same trigger in parallel without blocking each other or the trigger itself.

When to use this

When one event needs to reach multiple independent downstream systems that don't need to coordinate with each other.

How to use or implement this

Publish once (see CommunicationPatterns/PubSub) and let each consumer subscribe independently; make sure one consumer's failure can't block or slow the others.

Research questions

• Booking confirmed → email + SMS + analytics + provider notification, all independently and in parallel — a textbook fan-out.
• A 1000-device software upgrade dispatching PIV to run independently and in parallel across every device is fan-out at fleet scale — see RateLimiting/ for why 'in parallel' still needs a concurrency cap.

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Empty folder — drop notes, links, and findings here as you research.