Google App Engine or GAE or App Engine is a public platform as a service (PaaS), one of the service models of cloud computing as described by the NIST definition of Cloud computing. GAE was developed by Google and was made available for public usage in 2008. Its stable release is 1.8.2 in July 2013. GAE is written in Python, Java, Go, and PHP. GAE provides facility to develop and host applications in resources managed by Google. Entry level usage has certain restriction with free tier. App Engine provides free tier to get started. All applications can use up to one GB of storage and sufficient CPU and bandwidth to support a resourceful application serving around five million page views a month.
GAE supports Java, Python, Go, and PHP. It also supports other JVM languages such as Clojure and PHP via a special version of Quercus, JRuby, Groovy, and Scala by extension. GO and PHP are not in full fledged mode, they are in experimental phase. GAE makes it simple to build an application that is highly available and reliable even under huge demand with vast amounts of data requests. It provides automatic scaling and load balancing, persistent storage, full support for common web technologies, APIs for authenticating users and sending email using Google Accounts, full featured simulation of Google App Engine on your local development environment, scheduled tasks, and task queues.