I want to build mobile app. This app will connect to server, upload some data and files, server will perform some manipulation with data and files, and will send results back to app or to email. All server logic writen on java, there are several jars. So I need server. desirable flexible because i don't sure about possible popularity of app. So maybe cloud will be good solution. And i need suggestion, because i can't understand what i need, for example i looked on google side, but there are google app engine and google cloud what i need to choose? Or maybe select something other Amazon and etc.
Thanks