I need a web server to provide api interface like login/ranking for a mobile game, which web framework should I use, I primary program C++ before.
You should try out Firebase (https://www.firebase.com/) if you're looking for something relatively easy to store game data with. If you're looking for something to manage logins and storing simple data, either Twitter's Fabric (https://get.fabric.io/) and AWS Cognito (https://aws.amazon.com/cognito/) can also be used as well