Cache-aside with FastAPI and Redis: handling invalidation and concurrent requests

The article walks through the cache-aside pattern, where the application checks Redis first and falls back to the source of truth on a miss. It explains that writes update the source and delete the cached key so the next read repopulates it. The author demonstrates this with a FastAPI example using a simulated database with query counting, and tests that don't require a live Redis. It also describes the cache stampede problem, where simultaneous requests on an expired key all hit the database, and proposes a per-key lock with a double-check as a fix for a single process. Distributed locking in Redis is mentioned as an option for multiple instances, with the caveat of expiration trade-offs.