Save and load different variables for each player

What i would like to know is whether or not there is a simple way to save user data to a dedicated server, based on their account login. I would like players to have skill trees that are saved, and then used as variables for that player in game, I would like it so the players variables are unique to each person and they dont have access to modify/hack them. Ive got a base understanding of replication and saving, but i dont want to start scripting stuff and have it all be worthless.

Think of it like COD, after each game i want it to save the players stats, exp, and current weapon unlocks. Then when they start the game i want it to load that persons information for use during an actual match.