Found the problem. it was the plugin nodebb-plugin-merge-subtopics
It could load any category page with sub-categories in it.
Maybe it's hepfull for somebody who has same problem 🙂
i've seen articles stating that wp can run with big user spike and traffic on nginx 512mb without any problem so i would be very surprised if nodebb 500-1000 active users can't handle 512mb.
can anyone confirm or provide some figures?
I know that @scottalanmiller is running a relatively high traffic forum on nodebb.
A lot depends on various factors like if you're running a CDN, what plugins you're running, and any other processes running on the node.
On my setup, I was running a cluster of three, with a gocamo server, along with redis (for session storage) and mongo, along with (at the time) mysql.