Today's cloud offerings, while promising flexibility, fail to deliver this flexibility to lower-end services with frequent, minute-long idle times. We present DreamServer, an architecture and combination of technologies to deploy virtualized services just-in-time: virtualized web applications are suspended when idle and resurrected only when the next request arrives. We demonstrate that stateful VM resume can be accomplished in less than one second for select applications.

We have implemented DreamServer by customizing well-known open source software projects, the Apache web server and the virtual machine emulator qemu. Our evaluation of just how fast idle services can be reactivated includes different storage technologies, local and networked storage, and multiple VM resume strategies. The empirical results show that just-in-time deployment of virtualized services is possible with a minimal additional delay. This brings us closer to our understanding of flexibility in the cloud especially for customers with sporadic resource usage.