Hash slots

Redis Cluster uses 16384 hash slots. CRC16(key) mod 16384. Slots map to nodes. Reshard = move slots.

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Hash slots

Redis Cluster uses 16384 hash slots. CRC16(key) mod 16384. Slots map to nodes. Reshard = move slots.

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Client routing

Smart clients cache the slot→node map. On MOVED response, refresh. Dumb clients rely on proxy.

Replication + failover

Each master has 1+ replica. Sentinel or Cluster mode auto-promotes replica on master failure.

Cross-slot operations

MGET across slots requires touching multiple nodes. Use hash tags {user123}:profile to co-locate related keys.

Cache stampede

Popular key expires → 1000 requests hit backend simultaneously. Prevent with per-key locks or probabilistic early expiration.