Discourse is a pretty complicated piece of software (relatively). They do: mailing list, discussion forum, long-form chat room, This isn't gonna be some static blog, it's feature heavy. It needs redis, it needs some real-time chat capabilities etc etc. Also the choice to use a framework (Rails in this instance) was sound since it's complicated. So when comparing deployments you need to compare it to the php equivalent (Laravel). I think deployment and memory footprint are gonna be quite similar then.