I don't think web servers clarifies much, though. The most important web servers (Apache, nginx, ISS, etc.) are all written in C or C++, and they try to squeeze out every bit of performance they can. I guess we're talking about applications communicating over HTTP, but that's not my first thought when I hear someone talking about web servers without any more context.

(I'm aware of Caddy, but my understanding is that it's aiming for ease of use over performance.)