Don't know with what I mixed that up (POE, probably. I know, libev is only an option there). Not that libev is a rather huge software, it's basically a wrapper around whatever the host OS provides (select, epoll, kqueue). From looking at it, eventmachines's C extension does the same. So my main point stands: A big part of the performance characteristics of node come from a lower-level C functionality. I guess that having an infrastructure that's mostly asynchronous comes second. Pure V8 speed won't matter that much for most tasks. If someone has counter-examples, I'd be pleased to hear them. As often with concurrency, better memory efficiency would probably win out.