Not sure when this feature was released, but with 1.6 it appears to be available. The SDK includes a sample of PlayerDataStrorage, a complete project. The question is immediately, how can this be setup, and what needs to be configured.
So far I used Gamesparks, they have something called CloudCode, you send requests, trigger events, and a MongoDB is there to store runtime PlayerData. Thus, how can we send EOS queries from within the game, receive data, and we need to understand how can this be optimized.
Example how to update player data, basically calling the relevant values, collecting them in a string variable array, then sending this to the server for storage. Ideally you would update single array values.
And loading a specific value, so that we do not have to pull the entire player data all the time - the player data gets stored in an object, only updated when required: