Message brokers are specialised pieces of enterprise middleware designed to support integrating applications in a decoupled (in both time and location) manner, using messaging channels, implemented as either queues (for single consumer) or topics (for multiple consumers). Whilst deploying and operating a broker has an additional, ongoing cost for a business, if the scale of integration in your system and the non-functional requirements warrant it, they can can provide a flexible, better performing and more scalable solution than the alternative of implementing message queues in your database, especially, as is often the case, the latter is already overloaded.There are a considerable number of proven message brokers available today from a variety of vendors. Before committing to building your integrations on a particular broker, you should give careful consideration to how well it satisfies your requirements. I recently went through such an evaluation exercise, and ended-up choosing Amazon Simple Queue Service (SQS). While we haven’t regretted this decision, I did learn a few things along the way. In this post I’ll share a list of the functional and non-functional (technical) requirements that you should consider as part of evaluating a message broker, and also my opinion on how SQS measures up to other brokers in each case, and the trade-offs.

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