When building QR Connect, the goal was to create a frictionless bridge between physical spaces and digital commerce. The core problem was that setting up an e-commerce storefront is often too complex for small merchants, and checking out is too slow for on-the-go buyers. To solve this, I designed an API platform that automatically generates unique QR codes for businesses upon registration. When scanned, these codes take customers directly to the merchant's digital storefront.

I architected the backend using TypeScript, Node.js, and Express, adopting a clean, layered architecture to keep routing, business logic, and database operations distinct. Knowing that the system would handle sensitive financial transactions, I integrated both Stripe and PayPal. Rather than relying on synchronous API calls for payments, I implemented a robust webhook architecture. This ensures that order statuses and the internal business wallet balances are updated asynchronously and securely, even under heavy load. To prevent excessive calls to PayPal, I implemented a Redis caching layer for access tokens.

One of the most satisfying engineering decisions was offloading heavy tasks like sending transactional emails to background workers. I utilized BullMQ and Redis to create a reliable job queue, ensuring that the main API thread remains blazing fast for end-users. The result is a scalable, highly responsive backend that empowers businesses to sell effortlessly in the real world.