How would you design a distributed caching system like Memcached or Redis Cluster?

Architecture: client library for routing, cache nodes, cluster manager. Data distribution: consistent hashing with virtual nodes for balance. Replication: master-slave per partition for durability, async replication for speed. Cluster management: gossip protocol for membership, failure detection, automatic failover. Features: TTL expiration, eviction policies (LRU, LFU), memory management. Consistency: eventual for performance, read-your-writes via routing. Hot keys: local caching, key replication. Scaling: add nodes, automatic rebalancing. Monitor: hit rates, memory usage, latency percentiles.