I think the ultimate perfomance is found in pure java.nio/C/C++ solutions, but I think having a bit slower perfomance and higher abstraction is better since it

I think the ultimate perfomance is found in pure java.nio/C/C++ solutions, but I think having a bit slower perfomance and higher abstraction is better since it makes it much easier to maintain and debug the system. My general impression of java.nio is that it's very low-level and a generally hard to code against and it's the main reason why we didn't choose it. This said, I think node.js offers great usability while perfomance is pretty good. So if I was developing a new comet solution I would give node a go - you can always rewrite to something more low level once you begin to hit limits. IMO going after java.nio directly is a premature optimization and most projects won't hit limits with node.js.