[railsjedi]

Why would you dispute that the choice of technology affects performance? V8 is one of the fastest implementations of javascript. Combine that with a culture of nonblocking libraries, and it makes it very easy to write web services that scale for 99% of what developer's need.

Sure, if you hit it big, you'll probably need to change things around a bit. But I think its valid to say that with Node, you don't have to worry about performance because by default its really, really fast.

Overall I have mixed feeling with my experience with Node so far (the libraries are very young, and extremely flaky). However it makes it dead simple to write apps that scale to a ridiculous level without huge amounts of upfront planning.

[ericflo]

Performance is not the same thing as scalability. A hello world app with a 10 second pause is scalable, but replace that pause with a logging statement and you've just traded scalability for performance.

[railsjedi]

That's where the nonblocking comes in. It relates directly to scalability. It doesn't improve performance, but it allows more requests to come through while you are waiting for external resources like databases to return results (by far the most common cause of slowdowns on web servers).

Performance and scalability are not always a tradeoff. When you increase performance at the runtime level, you don't decrease scalability. However it allows you to serve more requests in the same amount of time.