Ooh, I might be able to handle this one!
The Player Data Storage is used to hold VERY small amounts of data that doesn’t get used to often in the game. Like maybe screenshots and such. This is because PDS saves THE ENTIRE FILE to their database (for some reason). AND it has very small read-write limits, so you can’t make use of them too often.
A RESTful api through Express.js is a very good start, but keep in mind EVERYTHING the players give you is the Devil’s Work. So, if the server is the player (which they are), it won’t be hard for them to modify values on their end with something like Cheat Engine BEFORE the api call is POSTed to save the data.
This is all speculation and I’m honestly guessing a bit because unreal engine takes too long to build to test this theory out and I already had to build it 13 times. If I’m wrong, DEFINITELY correct me on it!
I recommend building from source to be prepared for dedicated servers