Cloud Architectures are designs of software applications that use Internet-accessible on-demand services. Applications built on Cloud Architectures are such that the underlying computing infrastructure is used only when it is needed (for example to process a user request), draw the necessary resources on-demand (like compute servers or storage), perform a specific job, then relinquish the unneeded resources and often dispose themselves after the job is done. While in operation the application scales up or down elastically based on resource needs.
Example: an application that is currently in production using the on-demand infrastructure provided by Amazon Web Services. This application allows a developer to do pattern-matching across millions of web documents. The application brings up hundreds of virtual servers on-demand, runs a parallel computation on them using an open source distributed processing framework called Hadoop, then shuts down all the virtual servers releasing all its resources back to the cloud—all with low programming effort and at a very reasonable cost for the caller.
