question

It depends upon your requirements. A true tournament system would have a cut-off period for registration, some kind of ladder, and possibly wildcard match-ups for an underdog comeback (for a start). We do not currently provide a tournament system out-of-the-box. Depending on your requirements, you could build a "light" version of tournaments using our existing services, but if your requirements are more "full tournament system", you may need to look at incorporating additional features via your own custom servers, for example.

The systems we have which could be useful for "light tournaments" would be:

• Cloud Script or Custom Game Server Hosting - One way or another, you'll need to have server authority over the results of matches between players, so you'll want to use one of these to accomplish that.
• Leaderboards - These would be global to the game, and so isn't really applicable to the need for users to create their own tournaments. 
• Shared Group Data - If your tournaments are for 100 players or less, this could be a way to track on the status/scores of each player.
• In-app purchasing - We have multiple systems for purchasing items from your in-game catalog, both receipt validation and more cart-like sales. You could create consumable items which are used as the entry "token" to a tournament.