I'm certain there are other, far more valid reasons to migrate to Java, .net, Go, Rust or whatever. Rails' opinionated setup might simply not fit your use-case. Lacking language features (Interfaces, Typing, etc). Poor libraries(in your domain). Complex deployment- and operating stack. Too few good and experienced developers who know and like Ruby around and so forth and so on.
There are numerous reasons to move away from Rails and Ruby. Speed is but one. And often the easiest to solve in other ways.
¹ Actually, in my previous role as Rails consultant I often did performance tuning for Rails. 99.99999% of the times the executing time nor the GIL, nor the GC, are the problem. But the database is. Poor DBA, in my experience is the thing that makes most Rails apps slow. For which I blame Rails, because it makes it so damn easy to forego any sane design on the DBA, and just hobgobble together some `@user.devises.active.order(:used_at).messages.new` in your views, which fires the worst ever query on your database.
Sometimes.
But I'd urge you -and every Rails dev struggling with this- to look at how and where you can decouple and separate the concerns in your (quite likely) ball-of-models.
Most often that is a far more sustainable solution. One that helps you not only with performance.
Cost of development has always been the more significant cost over compute power for these businesses. Considering the entire web uses under 10% of the global energy rewriting your entire stack in c++ for the small performance improvement is not going to make a dent in that.
Why would businesses do this for such a small environmental improvement when they could spend half the money putting in solar and produce significantly more green energy than their stack uses?
Interesting, how do you know about this? I was under the impression GitHub were still mostly happy with Rails.
https://github.blog/2020-05-20-three-bugs-in-the-go-mysql-dr...
> Although GitHub.com is still a Rails monolith, over the past few years we’ve begun the process of extracting critical functionality from our main application, by rewriting some of the code in Go—mostly addressing the pieces that need to run faster and more reliably than what we can accomplish with Ruby.
In 2018 GitHub got acquired for 7.5 billion dollars. Rails got them to that point and they've been up and running since 2008. I'd say that's a very big success.
Given GitHub's contributions to Rails master and other activity around projects like https://github.com/github/view_component, from the outside it looks like they're still very happy with it. It's hard to say if we'd ever get a real answer on what they think internally, it would be pretty unlikely that their CTO is going to publicly write an official company blog post on "I wish we didn't choose Rails".
This isnt even mentioning the compelling environmental arguments against a computationally taxing dynamic language like Ruby, which is going to be louder in the next few years.