The MERN stack, comprising MongoDB, Express.js, React, and Node.js, is a robust framework for developing modern web applications. In this paper, we propose practical strategies to optimize MERN applications by addressing performance bottlenecks across the stack. Key techniques include indexing and query optimization in MongoDB, efficient middleware and routing in Express.js, and advanced rendering methods such as Server-Side Rendering (SSR) and React Server Components. Additionally, we explore the integration of GraphQL, TypeScript, serverless functions, and modern state management tools to enhance performance. By implementing these strategies, developers can improve speed, responsiveness, and scalability, ensuring a superior user experience. This paper serves as a comprehensive guide to building high-performance MERN applications using contemporary web development practices.