Component integration environments such as Microsoft .NET and J2EE have become widely popu-lar with application developers, who benefit from standardized memory management, system-wide type checking, debugging, and performance analysis tools that operate across component boundaries. This paper describes QuickSilver Scalable Multicast1 (QSM), a new multicast platform designed to achieve high performance in managed environments. Memory-related overheads and phenomena related to schedul-ing are shown to dominate the behavior of the system. We discuss techniques that helped us to alleviate these problems, and argue that they reveal general principles applicable to other kinds of high-data-rate protocols and applications in managed settings.