Massively multiplayer online games (MMOGs) are no longer a chimera. Everyday, new exemple of this application are released, available for free on the Web or on sale. Yet, high lags frequently affect MMOGs, annoying customers. This frustrating phenomenon is mainly due to the best-effort service provided by the Internet that is often responsible for congestion and loss of responsiveness. To address this challenging issue, we consider a mirrored game server architecture and present a mechanism aimed at accelerating the delivery of game events generated during game sessions. Our approach rests upon the use of an optimistic synchronization mechanism that exploits the semantics of the game to diminish the delivery time of game events, whilst maintaining the full consistency of the game state. Experimental results are reported confirming the adequacy of our approach.