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What is Redis Cluster, and what problem does it solve compared to running a single Redis instance? How does Redis Cluster automatically handle failover when a master node becomes unavailable? What are the key limitations of Redis Cluster that developers should be aware of compared to a single instance Redis setup? How do you monitor the overall health and status of a Redis Cluster to catch problems before they affect your application? How would you design a Redis Cluster deployment to properly balance high availability, performance, and cost for a large scale production application? What is a split brain scenario in the context of Redis Cluster, and how does the cluster protect against it?
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What is the difference between a master node and a replica node within a Redis Cluster?

Beginner

Answer

A master node owns a specific range of hash slots and handles both read and write operations for the keys in those slots, while a replica node keeps a synchronized copy of a specific master's data and can take over as the new master automatically if that master fails, providing both read scaling options and high availability.
-- Each master can have one or more replicas
redis-cli --cluster create node1:6379 node2:6379 node3:6379 replica1:6379 replica2:6379 replica3:6379 --cluster-replicas 1
Real-world example An online store runs a Redis Cluster with three masters and three replicas, one replica for each master, ensuring that if any single master fails, its replica can automatically take over without losing access to that portion of the data.

Common follow-ups: How many replicas per master is generally recommended for production?;Can a replica serve read requests while its master is still active?

Redis Replication;Redis Sentinel & High Availability
All 7 Clustering questions