Originally, for performance reasons. Async code lets you handle multiple concurrent connections without having to rely on multiple threads or processes (which a

Originally, for performance reasons. Async code lets you handle multiple concurrent connections without having to rely on multiple threads or processes (which are more resource hungry)[0]. Nowadays, there's also the fact that if you want to use Javascript on the backend, Node.js is the de facto standard. You don't necessarily have to do async I/O but you'd be fighting against the whole ecosystem by not doing so. [0] http://en.wikipedia.org/wiki/Preemption_(computing)#Preemptive_multitasking http://en.wikipedia.org/wiki/Preemption_(computing)#Preempti...