Simon Willison’s Weblog

Why is node.js so much faster?

My answer to Why is node.js so much faster? on Quora

There are two main reasons.

Firstly, Node runs on top of Google’s V8 JIT-compiled JavaScript engine, originally written for Chrome, which is extremely fast for an implementation of a dynamic language (faster than any of the various Ruby implementations).

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:

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.