The rapid growth of digital commerce has increased the demand for secure, scalable, and user-friendly online marketplace solutions. Traditional shopping systems often face challenges related to limited accessibility, inefficient product management, and restricted business reach. To address these issues, this paper presents the design and development of EcomNex, a scalable multi-vendor e-commerce platform developed using the MERN Stack (MongoDB, Express.js, React.js, and Node.js). The platform integrates customers, vendors, and administrators within a unified ecosystem, enabling efficient product management, secure user authentication, and centralized administrative control.

EcomNex provides dedicated functionalities for multiple user roles, including product browsing, vendor product management, category management, and platform monitoring. The system employs JSON Web Token (JWT)-based authentication and role-based access control mechanisms to enhance security and protect sensitive resources. MongoDB is utilized for flexible and scalable data management, while Cloudinary is integrated for efficient cloud-based image storage and retrieval. The React.js frontend ensures a responsive and interactive user experience across various devices.

Experimental evaluation demonstrates that the proposed platform effectively supports modern e-commerce operations by improving accessibility, usability, scalability, and operational efficiency. The modular architecture facilitates future enhancements such as payment gateway integration, recommendation systems, mobile application support, and advanced analytics. The study highlights the effectiveness of MERN Stack technologies in developing robust, scalable, and industry-oriented e-commerce applications.

Keywords—E-Commerce, MERN Stack, Multi-Vendor Marketplace, React.js, MongoDB, JWT Authentication, Cloudinary.