how do you manage state in real-time systems without losing your mind?

So, I'm stuck on state management for this real-time app. You know, the one with user sessions, live updates, and that collaborative editing feature. I was thinking about using Redis or maybe Memcached for caching, but I'm wondering if there are other ways to build this. What do you guys usually do for dynamic state in apps like this? Anything I should watch out for