While Web Services ensure interoperability and extensibility for networked applications, they also complicate the deployment of highly collaborative systems, such as virtual reality environments and massively multiplayer online games. Quite simply, such systems often manifest a natural peer-to-peer structure. This conflicts with Web Services' imposition of a client-server communication model, vectoring all events through a data center and emerging as a performance bottleneck. We design and implement the Kevlar system to alleviate such choke points, using an overarching network-overlay structure to integrate central hosted content with peer-to-peer multicast. Kevlar leverages the given storage and communication models that best match the respective information: data most naturally retrieved from the cloud is managed using hosted objects, while edge updates are transmitted directly peer-to-peer using multicast. Here, we present the Kevlar architecture and a series of carefully controlled experiments to evaluate our implementation. We demonstrate Kevlar's successful and efficient support of deployments across wide-area networks and its adaptivity and resilience to firewalls, constrained network segments, and other peculiarities of local network policy.