I tried Mastodon early on and it was pretty slow, which I assume is due to it being a Ruby on Rails app that probably wasn't heavily optimized. Probably also partly due to there only being a handful of popular instances so the inrush of users weren't being spread out very much. Anyone still encountering that? A fairly popular instance also crashed and lost all accounts, toots etc.: https://web.archive.org/web/2018032…
The choice of Ruby for a platform that is supposed to enable decentralization does not make sense. Most Ruby apps have tens to hundreds of dependencies and require a build environment which immediately limits access to a smaller group of developers familiar with Ruby build environments and debugging their way out of any dependency hell. Customization also becomes a problem. There is also no particular design in Masto…
Rails is performant, but like all languages and frameworks, if you aren't writing good code, it's going to be slow.