Not denying that Ruby is a perfectly fine choice but within the article itself it says that Stripe runs the world's largest Ruby codebase so certainly it might be testing the constraints of the language.

The thing I am interested is that I don't suppose that Stripe always had these many LOC's and so I would be curious to know if at any point as the codebase was increasing, were they looking at other new languages which were coming like golang or rust which was more suited for their work or not and what were there decisions/thinking process to continue using ruby.