What to use for large scale multiplayer?

SQL is generally your best option for large data storage. If you’re code oriented then SQL as a language is pretty easy to pick up.

If you’re not code oriented, You can still try to write your data with blueprints to a text file using (I’m pretty sure) Rama’s Victory Plug-in:

Try to match a file format like JSON or CSV, it’ll help to future proof your data if you decide to migrate your storage solution into SQL later; also it’ll be easier for others to read when either asking for help or expanding your team.

I’ve tried writing my own data storage solutions with just blueprints text parsing nodes, long before I knew any real programming, and it’s a real nightmare later when you don’t match a pre-existing standard.

Some pretty useful results just 1st page of google when searching for ue4 sql blueprints