A big problem with Discourse is that it's written in Ruby.
Ruby is 4-5x slower than PHP.. so what people who program in it do, is cache the heck out of everything.
It also uses substantially more RAM itself.. on top of what you are adding with in memory caches ( at a minimum, double your database size and put it in ram )
This is the case for a number of Ruby applications i've seen.. they can end up being very expensive to host and more difficult to diagnose.
Another big problem is that Ruby applications tend to be monoliths.. you get an error in one part of the application, and the entire system goes down.
Which is a HUGE stepdown from how PHP works ( only the broken code path breaks )
If you restart the app, it will take way longer to get back up than you expect. because it has to load and process the entire program.
I have a Ruby system here where the application is down for 2 minutes after i restart it due to the time it takes to reload..
Not cool.
From a end user perspective i like the Discord Stack Overflow format less than a traditional format.. so.. all downsides to me.
Flarum is Discourse's PHP equivalent and it's in an advanced state of development at this point.
Problem with it is that it's internally overly complex and uses uncommon 3rd party software, and a lot more things are a plugin than you expected.. so you'll have tons of plugins to maintain... and much likely, lower speed. ( AKA higher hosting costs )
Xenforo is really where it's at.. the worst part of it is that it uses Elasticsearch.. the best part is, well, everything else.
