PC Parts E-Commerce System Sequence Diagram maps five operational phases—authentication, product browsing, cart management, checkout, and chatbot interaction—across a Next.js frontend, Node.js/Express API, Auth Module, Product Management, Cart/Order, Payment System, Recommendation Engine, and MongoDB backend. User and Admin actors trigger sequences through the frontend, which communicates with the Express API to orchestrate authentication, product discovery with AI recommendations, shopping cart operations, secure payment processing, and real-time chatbot support. This architecture demonstrates separation of concerns, modular service design, and clear actor-to-system interactions essential for scalable e-commerce platforms. Fork this diagram on Diagrams.so to customize phases, add microservices, or adapt the sequence for your tech stack. The five-phase breakdown provides a reusable template for documenting complex multi-actor workflows in retail software.