Two-year-old venture-backed Skytap Inc, a University of Washington cloud infrastructure spin-out, says it’s got an API to enable “hybrid” clouds. Rather than use cloud computing in a silo, Skytap’s Web Services API and one-click VPN functionality create a situation where cloud resources are used as an extension of existing infrastructure.

The Seattle company says it’s not an all or nothing decision; companies can ease into the cloud without abandoning established processes and applications or rewriting code.

It imagines the cloud being used for large-scale testing and development.

Skytap’s Virtual Lab provides on-demand virtualized infrastructure like hardware, storage and networking, a lab management application and a pre-populated virtual machine library of major operating systems, databases and applications software.

It supports VMware and Xen and Windows, Linux and Solaris; it plans to support Hyper-V.

The start-up got a $6 million in A round from Madrona Venture Group, Ignition Partners, Bezos Expeditions and Washington Research Foundation a year ago.