FastAPI
PostgreSQL Locks
Redis
Celery
Scalable Multi-Vendor E-Commerce Backend
High-concurrency backend engineered with PostgreSQL row-level locks (select ... for update) to eliminate race conditions and inventory overselling during simultaneous flash-sale checkouts. Features Redis distributed caching, cursor-based pagination, and asynchronous Celery task pipelines. Stress-tested with Locust to sustain 1,000 concurrent users at 50 RPS with 0% error rate.