"I noticed that the vanilla mastodon server uses Ruby on Rails; and they picked Puma as their rack server which is a poor choice. I experimented by setting up a VM with common VPS specs and tested a single line change in the Gemfile and got massive performance and efficiency increases"
https://reddit.com/r/Mastodon/comments/18q2s05/i_noticed_that_the_vanilla_mastodon_server_uses/