Design a Distributed Cache System

Design a **distributed caching system** similar to Redis Cluster.

Include:
1. Sharding strategies (consistent hashing, slots)
2. Replication model
3. Gossip protocol membership
4. Eviction policies
5. Write-through vs write-back logic
6. Cache coherence handling
7. Failover strategy
8. Client routing mechanism
9. Metrics to monitor
10. Backup & recovery model