Suggest an editImprove this articleRefine the answer for “What does a replica do in a cluster?”. Your changes go to moderation before they’re published.Approval requiredContentWhat you’re changing🇺🇸EN🇺🇦UAPreviewTitle (EN)Short answer (EN)In Redis Cluster, a replica doesn't hold slots of its own - it copies its master's data (asynchronously, with no wait for acknowledgment) and can serve read requests when needed, taking load off the master; if the master fails, the replica is automatically promoted to master. **Key point:** every replica is tied to a single master and can't serve other masters' slots; writes always go through the master, so a replica doesn't acquire new slots on its own, it just mirrors what its master already has.Shown above the full answer for quick recall.Answer (EN)ImageIn Redis Cluster, a **replica** performs several key functions, but on its own it **doesn't hold any slots** - it copies its master's data. ### 1. Copying the master's data - A replica syncs with a master node and receives a **full copy of every slot** the master serves. - Replication is asynchronous: the master doesn't wait for the replica's acknowledgment when writing. ### 2. Providing fault tolerance - If the master fails, its replica is automatically **promoted to master**. - The rest of the cluster's replicas and nodes learn about it through **Gossip**. - That lets the cluster keep running with no manual intervention. ### 3. Scaling reads - Replicas can be used to **serve read requests**, taking load off the master. - Reading from replicas helps **scale throughput** without increasing load on the primary node. ### 4. Important points - Replicas **don't acquire new slots** on their own, they only copy their master's data. - Every replica is **tied to a single master** and can't serve other masters' slots. - A replica can have several downstream read clients, but writes always go through the master. ### Summary A replica in Redis Cluster: 1. **Copies its master's data**. 2. **Provides fault tolerance** (auto-failover). 3. **Scales reads**, reducing load on the master. > It doesn't hold slots itself, but it provides resilience and boosts the cluster's throughput.For the reviewerNote to the moderator (optional)Visible only to the moderator. Helps review go faster.