I’m confused. How do you expect to gain more performance from Rust? Rust and Crystal should be roughly on par performance wise. Both compile to a LLVM backend, so even the optimizations are pretty similar. There are some differences in the runtimes, but I’m not aware that makes a big difference. Many benchmarks show Rust and Crystal performing pretty similar. Even if one had a slight edge over the other, it would most likely not justify the overhead for switching to the other.
This could still be a fun endevour, I just don’t think this makes sense when you’re looking for performance improvement.