Backend service for asynchronous multiplayer games?

Does anybody know of a good and affordable backend service for asynchronous, turnbased multiplayer games?

I’m working on a two-player puzzle game and need features like user handling, finding opponents, friends list, rankings, highscores, messaging etcetera. Preferably with an SDK for Corona, but otherwise with a nice REST API.

 

 

I don’t want to use Game Center and Google Play Games since I think are too limited in features and not very user-friendly. I’d also love to have all players and statistics in one place regardless platform. 

 

 

/Markus