Very mature application web server engine. I made some examples using python with functionalities like excel export, pdf creation, openid authentication, RESTful service, database design (big table based). Overall an excellent approach to develop web services very fast and being prepared for mass usage if you like.
Unfortunately the authentication seams to be still very beta. It supports only OpenID but OpenID Connect would be much better as this supports oauth1/2 and OpenID.
The google cloud console is still very early but shows the direction it will go to.