[SideburnsOfDoom]

One of the benefits of "really functional" code is that without lots of side-effects and mutable state, it is easy to parallelise things. But if "you’re single threaded" as node.js is, you aren't going to get those benefits anyway, s it doesn't matter.

There are performance benefits to the asynchrony that node.js's callbacks give you - i.e. the single thread that you have doesn't block waiting for things to complete and can handle other requests in the meantime. But this isn't really parallelisation.