databases – How important is it to use an in-memory datastore for real-time networked game data?

I am building some online multi-player web-based games. Naturally, we are using WebSockets to connect to the game server. I need to store “real-time” data for these games, things like which users are in which games, each players’ score, whose turn it is, etc.

We have begun to use SQL for this type of data and I’m wondering if it’s a mistake.

I googled it a bit and it looks like the speed of SQL vs a key-value store is the same, but supposedly the CPU/memory needed for the SQL is way higher, and thus it’s a good idea to use an in-memory store.