Data centre, a popular form of hosting platform for Internet Services, rely on static centralized pools of servers. Although direct control over resources is advantageous here, these platforms are often unable to handle highly varying workloads. On the other hand, the peer-to-peer systems, harnessing idle resources from widely distributed computers, demonstrate the potential of these resources to build scalable, low-cost and easily deployable platforms. However, due to the uncertain availability of these resources, it is hard to provide any performance guarantee for the services. The primary contribution of the book is a new bi-modal architecture for a geographically distributed and cost-effective service hosting platform. The proposed architecture utilizes a combination of statically provisioned dedicated resource pools and opportunistically available inexpensive public resources to provide quality assured services. The core idea is that through dynamic management of the combination, one can gain from the scalability of the public resources and achieve assured quality services by masking their unreliable behaviour with the controlled performance of the dedicated resources.