Question: How can you manage TTL (Time to Live) in a Redis Cluster?

Answer

In Redis, the Time to Live (TTL) feature is used to set an expiration time on a key. In a Redis cluster, managing TTL is similar to a standalone Redis instance.

To set a TTL for a key in Redis, you use the EXPIRE command followed by the key and the number of seconds that the key should exist. For example:

EXPIRE mykey 60

This will set a TTL of 60 seconds on the key named "mykey". After 60 seconds, Redis will automatically delete this key.

To view the remaining TTL for a key, use the TTL command followed by the key name. For example:

TTL mykey

In a Redis Cluster, keys are partitioned across multiple nodes. Therefore, when setting or getting the TTL, you need to connect to the node which contains the key. If you try to access a key that's on a different node, Redis will return a redirection error with the address of the correct node.

It's important to note that if a master node fails and a slave takes over, all TTL settings will be preserved as they are part of the data set that gets replicated.

Also, while setting very short TTLs might seem like a good way to limit memory usage, it might cause unnecessary overhead due to constant deletion and creation of keys. So, consider your use case carefully before deciding on the TTL values.