I’m LAMP stack primarily, so somewhat biased, but for performance and scalability during high loads I’d recommend the admittedly expensive cloud database service by Rackspace.
https://www.rackspace.com/cloud/databases
In a nutshell, you get a dedicated server optimised for running a single MySQL instance (so tuned for high network load and fast read/write basically), and it comes pre-configured with as many replications as you ask for (think of a MySQL replication as working the same as a RAID set-up for disk drives - you’re writing to multiple copies and if any one goes down, it can be recreated from the others).
With Rackspace Cloud you set up whatever servers you want, however you want them. You could for example just have the one web server and host a single server side endpoint on that, and a local database. Or you could have say, 5 web servers hosting the same endpoint, all connecting to the same cloud database server (my above paragraph) and sit them all behind a load balancer that decides which server to pass the request through to based on all of their current loads. If your game takes off, simply duplicate those servers more.
For a proper, totally redundant set-up like that, you’d be looking at spending thousands, if not tens of thousands in USD/GDP per month, but you can start off small and expand to that over time, if the need arises.
We currently host about 80 websites of varying popularity, with about the same number of databases, on 2 relatively small cloud servers and pay about £180 p/m. We then host about another 30 very, very high traffic websites on a slightly bigger cloud server for I think about another £150 p/m. Combined traffic probably reaches about 1tb of monthly bandwidth, and the costs include nightly backups of all 3 servers to cloud storage (again for redundancy) where they sit for 30 days so we’re probably using about 1.5tb cloud storage space there too. Rackspace aren’t cheap, but we’re getting quite a lot there for £330 p/m and performance for us is fine, even without load balancers or dedicated database servers. Very nice to have the option of scaling up and adding those in.