MERN Stack RoadMap A complete RoadMap to MERN Stack. MERN Stack is a Javascript Stack that is used for easier and faster deployment of full-stack web applications. MERN stands for MongoDB, Express, React, Node, after the four key technologies that make up the stack. MongoDB - document database Express(.js) - Node.js web framework React(.js) - a client-side JavaScript framework Node(.js) - the premier JavaScript web server 3-Tier Architecture of MERN (frontend, backend, database).