Message Queues

A message queue lets one service hand work to another without waiting for it to finish.

A producer sends a message, the broker stores it, and a consumer processes it later. This decouples the producer from slow, restarting, or temporarily unavailable consumers.

This chapter focuses on classic queue-based brokers like RabbitMQ, Amazon SQS, and ActiveMQ.

It covers message delivery, acknowledgments, failed processing, retries, and dead-letter queues for messages that cannot be processed safely.