Creating a cross platform game needs starting help on the server side

Okay so I am creating a game this game is across multiple platforms.

The only thing that I can’t figure out because of lack of information is:

How can I create a server that handles all the data, by data I mean the entire save game, and most importantly how the server can handle all the ressources, for an example of the mechanics of gaining ressources you can take a quick look if you don’t already know at Clash Of Clans.

So, any help will be appreciated, and I am open to discussion