This is potentially a bad example, but the current "fastest" web frameworks as per the techempower benchmarks are all Java.

I'm not familiar with it, do you mean this one? https://www.techempower.com/benchmarks/

Rust, C, and Go appear to be on the top.

Sorted by full stack frameworks only: https://www.techempower.com/benchmarks/#section=data-r18&hw=...

They're not: C++ and Rust have winners for some of the tests.

Of course you can write more performant code with lower-level languages, though there is a reason that almost no web framework/application is written in them - the additional burden of managing memory outweighs the (actually surprisingly little) performance benefit. If you look at examples on the site, in basically every other benchmark Java and sometimes Go rank the best.

I should clarify that I sorted by fullstack frameworks with ORMs. Obviously C or C++ can be made faster.

Too late to edit now though.