PaaS is nothing but uploading your small kernel of code with business logic and the PaaS service provider will run that code on allocated computing and storage instances. The aim of PaaS is to let the developers concentrate on developing their code rather than creating and maintaining their ecosystem required for it. When Google launched App Engine in 2008 it had very basic functionalities but gradually it has evolved to support much good functionality like Channel APIs. But when it comes to language support, selection of cloud, selection of database, control over database, Cloud foundry gives great amount of flexibility as compared to App Engine. Also, when it comes to supporting Java packages also, Google App Engine doesn’t allow developers to free their arms as there are quite a few important packages which are still not part of App Engine’s white list.