Google app engine is my go to for web apps that need to be used in production at a small scale while I'm still evolving the functionality. What you prototype transfers into prod surprisingly well. The best part is I don't really have to worry about security - I just setup one of the default available authentication types and define access control in the routes in app.yaml. You don't have to be worried a hacking group…
I work on an open source implementation of it, so I'm always curious to hear about use cases and opinions.