"The Cloud" is a marketing hype term. It's basically the same old client-server architecture IT has been running for decades. They're just adding more to the server end now so there is much less, if anything, on the client end besides a browser. Kinda brings me back to the old mainframe days, when all you had in front of you was a dumb terminal.
Their "scalability" is still limited by the number of servers they have to support that application, but in the end no matter how you slice it, it's still good old fashioned client-server architecture.
If you want to create a virtually unlimited multiplayer interactive environment (an MMO basically) there are a few different ways to accomplish it, but my personal favorite is...
- A backend database server (or server cluster if necessary)
- As many servers as you need to meet the needs of the number of players you anticipate
- A server director application to direct incoming player connections to an available server
The server application would then get it's data from the database backend, and would have to share data across a high speed network link to keep players updated about players near them that may not be on the same server. Even with this, the link between client and server reaches a saturation point where you can't deal with the amount of data needed to keep updates flowing. You can ease this in the same way that WoW does by only sending updates for players that are within a certain range of that client, but there would still be a big problem if 10,000 players decide to go into the same area at the same time. The performance of the player's computer, their internet connection speed, and internet performance between them and the server will impact all of this.
The client, is nothing more than a communications tool to talk to the server, and display whatever it is you tell it to display. Whether that's DirectX graphics using DBPro, a Flash game interface like the Unity Web Player, or a screen full of text makes little difference.
MMOs, for these reasons and more, are the hardest type of game to write.
