There's nothing in node that provides mechanisms for cross process scalability. Compared to Erlang, for instance, which provides mechanisms for message passing and scaling past one node, and even one node can efficiently use multiple cores. Node is quite fast but not scalable in that sense.

So last time I looked at it, Node.js did not have any language level or even library primitives for message passing. At least nothing beyond making you open a socket and work out your own protocol for IPC. I'll grant you that is the standard scalability story for most languages running on multiple hosts. However it seems deficient if one's goal is to make use of most of the cores on modern server hardware.

Your OS's copy-on-write page policy loves when you fork things using mark-and-sweep garbage collection. It is full of rage.

Last time I checked Node.js was not able to invoke fork.