Why is node.js so much faster?
My answer to Why is node.js so much faster? on Quora
There are two main reasons.
Secondly, Node emphasises callback-based asynchronous IO and makes it very hard to make blocking calls. For web apps that spend most of their time waiting on network or database connections this can be a lot more efficient: http://code.danyork.com/2011/01/...
Ruby can do asynchronous IO using EventMachine or similar but you have to specifically work for it—with Node you get that behaviour by default.