Modern Web sites provide multiple services that are often deployed through distributed architectures. The importance and the economic impact of Web-based services introduces significant requirements in terms of performance and quality of service. In this paper, we describe the necessary load monitoring, dispatching and access control mechanisms that allow the architecture to achieve graceful degradation even in the case of unpredictable and overwhelming user request loads. The implemented access control strategy aims to favor the completion of already initiated user sessions, with respect to requests pertaining to new sessions.