Secure MERN stack architecture integrating eSewa payment gateway for e-commerce and SaaS platforms. React.js client communicates with Node.js/Express.js API server, which manages MongoDB Atlas database operations and eSewa payment transactions. This three-tier pattern isolates presentation, business logic, and data layers, enabling independent scaling and security hardening. Fork and customize this diagram on Diagrams.so to match your deployment topology, add load balancers, or extend with additional microservices. The architecture demonstrates secure payment flow separation, keeping sensitive eSewa credentials server-side while maintaining responsive client-side user experience.