Wow am I glad I walked away from the discourse community and never looked back! That is overly complicated. Why would they recommend a 100+ GB DB instance for running discourse? I can't find any reasoning in that at all. Show me a forum with 100GB needs on their database. Surely they're one of the largest in the world.
In general, memory requirement is much less. I think discourse still recommends 1GB+, that would be equivalent to 512MB for Flarum. Both will run, but you'll need to use swap. Discourse will need it pretty much right away for the app itself, and Flarum will need it to install with composer. Flarum actually does quite well outside of the install on 512MB.
Additional differences are discourse running redis server, you don't use that here. You don't use postgres, you'll use mysql or mariadb. You can have a running Flarum on a nano EC2, and if you want to speed things up get a nano for DB, and a nano for the app. If you need to scale up, that's not really an issue with AWS.
