Caching

Serving reads in under a millisecond and shielding the database from the load: sharding, eviction, hot keys, and stampede protection.

Explainers

• Design a Distributed Cache — Start with one cache box in front of the database; end with a fleet that survives a celebrity post pulling 300k requests a second at a single key. How keys spread across machines, what gets evicted when memory fills, and the defences for when one key goes nuclear — drawn and computed.