You can find some benchmarks here: https://github.com/kostya/benchmarks
With the caveat of course being that benchmarks don't always reflect real world performance.
Also Crystal based web frameworks tested here (key: Cry) same caveat as above. https://www.techempower.com/benchmarks/
Re:Crystal 1.0 – What to expect
by weatherlight on Monday March 22, 2021 @07:09PM
(#26548693)
It's at least on par with Go, for solving similar problems, micro benchmarks, etc.
So what is the performance like?