HTTP caching, cache-aside, write-through, Redis patterns, and cache invalidation — plus the stale data problems. The Request That Cost $100,000 In 2017, a major cloud provider experienced an outage that traced back to a single misconfigured cache. A caching layer that was supposed to serve data within 5 milliseconds had been configured with a TTL (time-to-live) of 24 hours. When the underlying database was updated at 2:00 PM, the cache continued serving the old data until 2:0...