ecommerce backend is an experimental, highly concurrent order processing and payment service. It leverages an event-driven architecture to coordinate inventory updates, checkout processes, and payment status updates asynchronously.
Most web developer tutorials show monolithic ecommerce services that quickly break under heavy load or network partitions. I wanted to design an decoupled architecture that models how real-world scale works: checking out is asynchronous, and the user's interface updates via webhooks or polling. I chose PostgreSQL for its strong ACID properties and RabbitMQ because of its flexible routing and high reliability guarantees.
Managing distributed state was a massive challenge. Specifically, preventing race conditions where multiple checkout events try to purchase the same inventory item at once, or handling situations where Stripe processes a payment but the user closes the window. I implemented pessimistic locking on critical database records during checkout, and built idempotent event consumers to prevent duplicate processing.