Suggest an editImprove this articleRefine the answer for “How does replication affect performance?”. Your changes go to moderation before they’re published.Approval requiredContentWhat you’re changing🇺🇸EN🇺🇦UAPreviewTitle (EN)Short answer (EN)Replication in Redis both helps and complicates performance depending on which side you look at: reads speed up (replicas handle read requests, taking load off the master), writes slow down slightly (the master streams changes to every replica), and the network gets more loaded. **Key point:** because it's asynchronous, a replica can lag behind the master by fractions of a second or more, which doesn't affect the master's speed but reduces data consistency when reading from replicas; overall, replication makes the system scalable and resilient, and its impact on the master is kept minimal.Shown above the full answer for quick recall.Answer (EN)ImageReplication in Redis **both helps and complicates** performance, it all depends on which angle you look at: reads, writes, or the network. ### 1. Reads, get faster - Replicas can serve **read-only requests**, taking load off the master. - With a lot of clients, the load can be split: ```javascript master → writes only replicas → reads only ``` - That scales the system horizontally and increases overall throughput. **The takeaway:** replication significantly improves read performance. ### 2. Writes, slow down slightly - The master has to **stream changes** to every replica. - That takes network resources and a bit of CPU time. - With more replicas, load on the master grows proportionally to their number. **The takeaway:** as the number of replicas grows, the master can slow down from distributing the data. ### 3. The network, gets more loaded - Every update travels over the network to every replica. - If there's a lot of data (large keys, frequent writes), traffic can become noticeable. - With cascading replication, some of that load can be redistributed. **The takeaway:** the network is the main bottleneck when data volume is large. ### 4. Latency between nodes - Because of asynchrony, a replica can **lag** behind the master by fractions of a second or more. - This doesn't affect the master's speed, but it reduces data consistency when reading from replicas. ### Summary: Replication **speeds up reads**, **slightly slows down writes**, **increases network load**, but overall makes the system **scalable and resilient**. In Redis, it's optimized to keep the impact on the master's performance to a minimum.For the reviewerNote to the moderator (optional)Visible only to the moderator. Helps review go faster.