nestjs/nest

NestJS is a framework for building the server-side, also called the backend, of web applications using JavaScript or TypeScript. The problem it solves is architectural: while Node.js (the runtime that lets JavaScript run on a server rather than just in a browser) has many useful libraries for handling web requests, those libraries do not tell you how to organize your application. Large projects built without a clear structure tend to become difficult to maintain, test, and scale. NestJS imposes a clear, opinionated architecture out of the box. The framework is deeply inspired by Angular, a popular frontend framework, and borrows its core concepts. You organize your code into Modules (self-contained feature units), Controllers (which receive incoming requests and return responses), and Providers or Services (which contain the actual business logic). This separation makes it clear where different responsibilities live. NestJS also uses decorators, a TypeScript feature where you annotate a class or function with metadata, to declare routes, inject dependencies, and configure behavior without writing a lot of boilerplate setup code. Under the hood, NestJS builds on top of Express, a widely used Node.js HTTP library, or optionally Fastify, a faster alternative. It supports building REST APIs, GraphQL APIs (a query language for APIs), real-time applications using WebSockets, microservices (a style of architecture where an application is broken into small independent services), and message queues. You would use NestJS if you are building a production-grade backend that needs to scale, be tested rigorously, and be maintained by a team over time. It is especially common in enterprise environments. The stack is TypeScript running on Node.js, installable via npm.