The design of massively multiplayer online games (MMOGs) is challenging because scalability, consistency, reliability, and fairness must be achieved while providing good performance and enjoyable gameplay. This article presents Journey, an MMOG middleware that hides the complexity of dealing with the aforementioned issues from the game programmer. Journey builds on top of a peer-to-peer network infrastructure to provide load-balancing, fault-tolerance, and cheat-detection capabilities centered on object-oriented technology. Experimental results show performance measurements obtained by running Journey on more than 200 machines.