Hi, First you have to choose a platform for your backend. It can be a plain web server with php scripting, Amazon EC2 or Google App Engine. These are just a few choices out of many but it really depends on your goals and limitations of your project. I have developed a multiplayer poker game based on appengine so I can speak to that platform. To work with GAE you need to know Java or Python. GAE is pretty a powerful cloud platform. It is main feature is they provide very substantial scalability coupled with almost zero maintenance effort. Let me know what you are looking for. Maybe I can answer with some more details.