Implementing an LRU Cache with Redis

Caching Policy

We have developed a system that uses Redis to cache query results from the database. However, this system is not very efficient because it simply saves each result to the Redis cache and keeps it there indefinitely. This can lead to the cache using up all of the computer’s available RAM over time.

To solve this problem, we need to delete some of the items in the cache and only keep the ones that are most likely to be read again. One way to do this is to implement an LRU (Least Recently Used) caching policy, which deletes the items in the cache that were used the least recently.

Fortunately, Redis already includes an LRU mechanism, so we don’t have to worry about implementing it in the application layer. Instead, we can simply configure Redis to delete items using an LRU policy. To do this, we just need to add two arguments to the command that starts Redis. The first argument limits the amount of memory Redis can use (in this example, we’ve chosen 512 MB), while the second argument tells Redis to use the LRU policy. The command will look like this:

redis-server --maxmemory 10mb --maxmemory-policy allkeys-lru

By using this configuration, we can ensure that our Redis cache remains efficient and doesn’t use up all of the available RAM.