Cloud Computing is a revolution in computing architecture, transforming not only the “where” (location) of computing, but also the “how” (the manner in which software is produced and the tools available for the automation of business processes). Cloud Computing emerged as we transitioned from an era in which underlying computing resources were both scarce and expensive to an era in which the same resources were cheap and abundant. There are many ways to implement Cloud architectures, and most people are familiar with public cloud services such as Gmail or Facebook. However, much of the impact of Cloud Computing on the economy will be driven by how large enterprises implement Cloud architectures for their own private use. Lead users are already combining private and public computing resources into new hybrid delivery models. Cloud architectures are also poised to disrupt the Information Technology (IT) industry, broadly conceived, with a new wave of commoditization. Offerings optimized for high performance in an era of scarcity are giving way to loosely coupled, elastically managed architectures making use of cheap, abundant computing resources today.