Anypoint MQ implements publish/subscribe fan-out by publishing a message to a message exchange and binding multiple queues to that exchange. Each subscribing application consumes from its own queue. As a result, a single gate-change event published by the Flight Management System can be copied to the Baggage Handler, Inflight Catering, and Passenger Notification queues independently.

MuleSoft documents that messages sent to an exchange are delivered to its bound queues and specifically describes exchanges as the mechanism for distributing one published message to multiple applications. A consumer does not directly consume from the exchange; consumption occurs from a queue. In fact, MuleSoft states that attempts to consume from a message exchange are rejected because the destination for consumption must be a queue.

Having all systems consume from one queue would instead create competing consumers: individual messages would normally be processed by one consumer rather than independently delivered to every subscribing system.

The required architecture is therefore: publisher → exchange → multiple bound queues → independent subscribers. This supplies asynchronous fan-out while preserving subscriber isolation and independent consumption.

Reference topics: Anypoint MQ exchanges; queue bindings; publish/subscribe; asynchronous event distribution.

Official documentation: https://docs.mulesoft.com/mq/

Official documentation: https://docs.mulesoft.com/mq/mq-exchanges

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