Developed scalable full-stack applications using the MERN stack (React, Node.js, Express, MongoDB), delivering an e-commerce platform and an appointment scheduling system used for real-world production workflows. Engineered core features including product browsing, order placement, booking workflows, admin dashboards, and delivery tracking, improving overall user interaction and operational efficiency. Improved frontend performance by implementing React lazy loading, reducing initial page load time by 22% and enhancing perceived responsiveness. Designed and optimized RESTful APIs with efficient MongoDB indexing, schema optimization, and pagination, improving API/database response times by approximately 30%. Implemented secure JWT-based authentication and role-based access control, strengthening application security and enabling differentiated user permissions. Built business-centric features such as coupons, referrals, loyalty rewards, advanced search, and user profile management, improving platform usability and engagement. Deployed applications on AWS EC2, conducted API validation and performance testing, ensuring stable production releases under concurrent usage.