MERN

MERN refers to a modern JavaScript-based full-stack for building web applications, comprising MongoDB, Express.js, React, and Node.js. The stack uses JavaScript across the client and server, enabling a cohesive development experience and a shared data format such as JSON.

MongoDB is a document-oriented NoSQL database that stores data in flexible, JSON-like documents. It is designed for scalability and rapid development, using BSON for storage and supporting dynamic schemas.

Express.js is a minimal, flexible web application framework for Node.js. It provides routing, middleware, and utilities to build servers and APIs efficiently, serving as the backend layer in a MERN app.

React is a front-end library for building user interfaces with reusable components. It renders in the browser and supports client-side rendering, with options for server-side rendering or hydration to improve performance and SEO.

Node.js is a JavaScript runtime that executes code on the server. It uses an event-driven, non-blocking I/O model, enabling scalable network applications and a unified language environment for full-stack development.

In a typical MERN application, a React frontend communicates with a backend API built with Express and Node, which in turn queries MongoDB to persist or retrieve data, often exchanging JSON payloads. The stack benefits from a unified language, a large ecosystem of npm packages, and streamlined tooling for development and deployment.

Limitations include potential complexities of NoSQL data modeling for highly transactional workloads, and the need to manage client-side rendering implications for search engine optimization. MERN is often contrasted with MEAN (Angular) or MEVN (Vue) stacks.