Clickbait title aside, use whatever language will make you and your team most productive to launch your product, if you run into issues once you hit it big concern yourself with "web-scale" then.
In 15 years of coding I've run into extremely few web dev projects that tree profiling to find the issue then caching hasn't solved.
In 15 years of coding I've run into extremely few web dev projects that tree profiling to find the issue then caching hasn't solved.