Simple use cases for message queues in a web application include: - Improving response latency by moving deferrable tasks out of the page serving code - Impro

Simple use cases for message queues in a web application include: - Improving response latency by moving deferrable tasks out of the page serving code - Improving response latency by simplifying implementation of concurrent tasks (whether across cores or servers) - Allowing capacity planning for average load instead of peak load for deferrable tasks The bigger story is that message queues make a good substrate for building fault-tolerant, highly available, scalable distributed systems that are easy to reason about and have predictable performance. This is because system components can be cleanly decoupled, implemented with redundancy and scalability, the message queue itself takes over much of the complexity of failover and delivery/ordering guarantees, and the message queue makes an excellent point for monitoring the system, giving visibility into logjams and problems in a live system.