Large-scale multiplayer online games require considerable investment in hosting infrastructures. However, the difficulty of predicting the success of a new title makes investing in dedicated server and network resources very risky. A shared infrastructure based on emerging on demand computing models to support multiple games offers an attractive option for game providers whose core competency is not in managing large server deployments. In this paper we describe a prototype implementation of a service platform for online games. The platform design follows the on demand computing paradigm by embracing integration using open standards and off-the-shelf software, and virtualization and simplification to enable sharing of resources across games. We describe our experience identifying appropriate performance metrics for provisioning game servers and implementing reusable platform components that provided useful functionality for a variety of games.