A MEAN stack developer is a software developer who specializes in working with the MEAN stack, a set of technologies used to build dynamic web applications. "MEAN" is an acronym for the four main technologies that comprise this stack:

MongoDB: A NoSQL database used to store data in JSON-like format. It is highly scalable and flexible for handling large amounts of data, particularly unstructured data.

Express.js: A lightweight and fast web application framework for Node.js. It simplifies the process of handling HTTP requests, routing, and middleware management.

Angular: A front-end framework developed by Google. Angular is used to build single-page web applications (SPAs) and provides a robust set of features such as two-way data binding, dependency injection, and powerful templating.

Node.js: A JavaScript runtime built on Chrome's V8 engine. It allows developers to execute JavaScript code server-side, enabling them to build fast, scalable, and real-time web applications.

Key Responsibilities of a MEAN Stack Developer:

• Front-end development: Using Angular to build dynamic, responsive user interfaces (UI).
• Back-end development: Writing server-side code in Node.js and using Express.js to handle client requests, manage routing, and implement business logic.
• Database management: Managing MongoDB to store and retrieve data efficiently and working with schemas.
• End-to-end development: Developing full-stack web applications where a developer manages both the front-end and back-end of the application.

Skills and Tools:

• JavaScript: Since MEAN is a JavaScript-based stack, knowledge of both client-side (Angular) and server-side (Node.js, Express.js) JavaScript is crucial.
• TypeScript: Although not mandatory, TypeScript is often used in Angular for type safety.
• Version Control: Familiarity with version control systems like Git.
• API development: Knowledge of RESTful APIs, which are often built using Express.js in the MEAN stack.
• Testing: Understanding of testing frameworks like Jasmine (for Angular) and Mocha/Chai (for Node.js).
• Deployment: Knowledge of deploying web applications using cloud platforms like AWS, Heroku, or traditional web hosting services.

Advantages of the MEAN Stack:

1. Single language across the stack: Since JavaScript is used both on the front-end (Angular) and back-end (Node.js), developers can work with a single language throughout the development process.
2. Scalability: MongoDB is well-suited for handling large datasets and scaling horizontally, making it a good choice for high-growth applications.
3. Real-time application support: With Node.js, MEAN stack apps can handle real-time data, which is great for applications such as messaging, notifications, and live updates.
4. Community support: All technologies in the MEAN stack have strong developer communities, which makes finding solutions and resources easier.

A MEAN stack developer needs to be versatile, as they work with all aspects of the web application, from database management to server-side logic to creating a seamless user experience with the front-end.