How would you design a cache system?

I would begin by clarifying access patterns, data volatility, and consistency requirements.

At a high level, the system would include a fast in-memory cache layer such as Redis in front of the primary database. I would define an eviction policy like LRU to manage memory usage and implement TTLs for data freshness.

I would also plan for cache invalidation strategies, cache stampede protection, and monitoring of hit rate. The design trade-off typically balances freshness, consistency, and performance.