You are focussing too much on the language and scalability rather than focusing on just building something. Every major language/framework out there has been u

You are focussing too much on the language and scalability rather than focusing on just building something. Every major language/framework out there has been used and scaled for large websites. Pick one that you would like to learn, provides you with the flexibility you are looking for, and run with it. Worrying about how you will scale an app that you have not built yet will be a major drawback. Also keep in mind performance and scalability as you're building the site, but do not spend much time worrying about it before hand. Just take an idea and run with it, tweak the app to scale as you go.