Shopify is absolutely a Ruby / Rails company. If out of the thousands of developers that work there you have a team or two writing some performance heavy c++ / Go code that says absolutely nothing.
Wouldn't it actually say a lot? Engineering is about trade-offs, and the trade-off that says "use this special language for 1% of our most critical services instead of the company-wide standard language" is not "absolutely nothing".
Lines of Code is a bad proxy for mission critical.
All of Shopify is mission critical. The code that constitutes the Shopify monolith is mission critical for sure. The company won't function without it.
This is somewhat circular, but: when your team decides to rewrite a component in a more complicated or more obscure (at least at Shopify) language to increase throughput rather than spinning up more instances of the current solution, then you're talking about a component that's even more critical than the other critical components.
It's just common practice - in Ruby some popular gems that parse XML or JSON come with a C extension that does some performance heavy calculation. Most gems don't do this, but when performance is very important some do.
Us Rubyists see no problem with that, and we don't take this as some kind of incentive to leave Ruby, maybe even the opposite; knowing that you can do 99% of your app in Ruby, and if ever needed, easily fill in the 1% with Rust/Go/C++ is very reassuring imo.
