And that's why I love Node.js: the single-threaded concurrency (or should I say non-concurrency?) is built-in in the execution model. Building your architecture decoupled from the ground up is useful, and Node.js does a great job at it.

I found Redis is an awesome middleware for MQ purposes. Its builtin PubSub system, blocking POPs and amazing speed make it a perfect fit.

But beware: it's easy to get it wrong and make the system a tangled mess of messages. Just make sure the message dispatch overhead is worth it.