Some years ago I had a C# program that was taking too long to finish. The time required for it to finish processing was approaching a minute. For an interactive program, this was not acceptable, so I focused on optimizing the program.
Eventually I added multi-threading to the program, and it finished in less than 100 milliseconds. However, I was still curious as to whether other languages, like Go or Rust, could be faster than C#.
I ported the program to Go, and although I changed the algorithms a bit to be more efficient (this often happens when porting) the program was at least 20% faster, even without any optimization-specific work. The Go program took 80 milliseconds to finish.
Finally, I ported the Go program to Rust, and surprisingly this version was not only plagued with fewer bugs (it worked correctly right away), but it also was twice as fast as the Go version, at 40 milliseconds.
In the comparison of C#, Go and Rust, I found that C# and Go were similar, although Go was faster for command-line programs as it was compiled ahead-of-time. Rust meanwhile was the fastest programming language to use, and this was before any optimization work was done—it was just the first compiling version.