Why is uneven load observed on different Redis Enterprise shards?

Question

Why is uneven load observed on different Redis Enterprise shards?

Answer

Having more shards for a database to exploit parallelism offered by multiple cores is possible, but it may not always help. There could be a few reasons for having a hot shard. One is that there is a big key or keys on that shard. To find that you can run the redis-cli command with --bigkeys flag.

redis-cli -h <hostname> -p <port> -a <password> --bigkeys

You could also have a hot key. In order to identify that you could run the MONITOR command for a very short monitor period of time (a few seconds) in a low-traffic period. Please note that this command is dangerous and can affect latency. Please run it for a very short period of time and test it out first on a dev DB or other low-traffic non-production DB. Read more here.