[9876543210]

I thought node's non-blocking I/O implied that threads were unnecessary?

What's the core mechanism that permits node's implicit concurrency?

[Cthulhu_]

It is, but that also means a Node application will not use all four cores of a quadcore efficiently by default. I think the usual approach in that case is to just rev up four node processes with a load balancer of sorts in front of it.