Like one of the former engineers at Twitter said about their early issues with stability and when someone blamed Ruby for the performance issues - short version it was a bad architecture not the language.

Stateless web servers are one of those things which are ridiculously and easily parallelizable, you can scale a web server horizontally easily. The ROI of rewriting everything in another language as opposed to just adding more web servers would probably take years unless you’re running at a ridiculously large scale. For the cost of one developer’s fully allocated salary, you can throw a lot of hardware at performance issues with web apps.

I prefer statically typed languages, but performance isn’t one of them. Besides, how much processing is a typical web app doing?