Until 2010, most orgs constructed and maintained own computing infrastructure: purchased or leasd hardware, installed on their premises, used it to support organizational email, websites, ecommerce sites, inhouse apps. After 2010, orgs began to move computing to the cloud. Cloud = elastic leasing of pooled computer resources over the internet: elastic computing resources leased can be increased or decreased dynamically, programmatically in short span of time and orgs pay for just resources they use. Cloud vendor can provision servers worldwide using the cloud. Don"t need to build or contract for infrastruct that supports maximum demand that may leave servers idle: pooled many diff orgs use same physical hardware; share that hardware thru virtualization, over the internet. Cloud vendors allocate virtual machines to physical hardware as customer needs incr/decr. Cloud vendors benefit from economies of scale avg cost of production decr as size of operation incr. Service-oriented architecture (soa) way of designing computer programs so they can be flexibly combined.