Comment by resca79

Really strange that how back-end developer you never had a use-case for Redis yet.

First you could check at

https://redis.io/topics/data-types-intro

If you look at single data type you can see how redis takes care about complexity(indicating the Big O notation) of each single data structure and operations.

Many devs use it for caching but in my opinion is super nice for evil-write applications.