Node.js is designed to build scalable network applications.
Node.js is similar in design to, and influenced by, systems like Ruby’s Event Machine and Python’s Twisted. Node.js takes the event model a bit further. It presents an event loop as a runtime construct instead of as a library.
HTTP is a first-class citizen in Node.js, designed with streaming and low latency in mind. This makes Node.js well suited for the foundation of a web library or framework.
Node.js being designed without threads doesn’t mean you can’t take advantage of multiple cores in your environment. Child processes can be spawned by using our child_process.fork() API, and are designed to be easy to communicate with. Built upon that same interface is the cluster module, which allows you to share sockets between processes to enable load balancing over your cores.