Maybe not the best testimonial. From what I've heard, Mastodon is a bit of a beast to scale. While some of this is probably due to ActivityPub (a la https://lucumr.pocoo.org/2022/11/14/scaling-mastodon/) itself, some of it may be related to Ruby's execution model: https://lukas.zapletalovi.com/posts/2022/why-mastodon-instan...

My issue with Ruby (and Rails) has always been the "ball of mud" problem that I feel originates from its extensive use of syntactical sugar and automagic.