This document discusses building scalable network applications using Node.js. It begins with an introduction to Node.js, describing it as a software platform built on the Chrome V8 engine for building scalable applications using JavaScript on the server side. It then discusses why to use Node.js, noting that its single-threaded and event-driven model avoids issues with memory usage that can occur in multi-threaded models. The document proceeds to explain event loops and non-blocking I/O in Node.js. It then provides an example of building a simple web server with Node.js. Finally, it introduces Express.js and provides an overview of how to structure an Express application using MVC patterns with models, views,