Node.js is an open source, cross-platform runtime environment for server-side and networking applications. Node.js applications are written in JavaScript, and can be run within the Node.js runtime on OS X, Microsoft Windows, Linux and FreeBSD. Node.js provides an event-driven architecture and a non-blocking I/O API that optimizes an application’s throughput and scalability. These technologies are commonly used for real-time applications. Node.js uses the Google V8 JavaScript engine to execute code, and a large percentage of the basic modules are written in JavaScript. Node.js contains a built-in library to allow applications to act as a Web server without software such as Apache HTTP Server or IIS. Node.js is gaining adoption as a server-side platform and is used by Groupon, SAP, LinkedIn, Microsoft, Yahoo!, Walmart, Rakuten and PayPal.