Real world example for Crystal: our overnight sitemap generation (built using Ruby, as part of our Rails app) took 6 hours to generate 20 million links. At some point due to infra changes, it stopped running to completion. Since then, we ported it over to Crystal, with the main code virtually unchanged (library to help generate sitemaps has matching API). Just had to set up basic database mapping for a few tables. That version is now in production, and it now processes 30 million links in about 30 minutes.
Since a library is mentioned, it is possible that the Ruby library was particularly inefficient compared to Crystal. Crystal is definitely faster than Ruby, but I expect differences to diminish in IO-bound operations (which sitemap generation sounds like it would be).
It's not specifically Ruby, but also using ActiveRecord, loading bloated models, associations, and some business logic. There is also a large amount of memory bloat with the sitemap library when working with large datasets. The Crystal sitemap library has a way to avoid that same bloat.
With Crystal, all of those things are massively faster.
Crystal performance is close to Go-lang. It's just very fast across the board.
Consequently, just like Go-lang, it beats Ruby by an order of magnitude on pretty much any benchmark.
Newcomers often assume Crystal must be sluggish like Ruby because "how could a language with such a convenient syntax be so fast", but it really is not.
in fact Crystal concurrency is the same with Go, both using coroutine technique.
though Go should be more performance because it is built for that feature.
The biggest thing is the massive speed improvement compared to working with bloated ActiveRecord models, associations, plus some memory bloat. The Crystal implementation is massively fast dealing with database data.
