Our official install guide lists 1GB of RAM (+2GB swap) as the minimum requirements for Discourse. This is still possible, but over the last few months it has become increasingly painful to rebuild Discourse with servers of this spec. This is primarily because of changes to our JS build tooling.
We’ve just landed these tweaks, which should significantly improve rebuild times on low-memory servers:
https://github.com/discourse/discourse/commit/9db5eafb15688cf0604805fb5b315efca1c712a6
Given the number of variables it’s hard to promise exact numbers. But, in my tests on a DO droplet with 1GB RAM (+2GB swap), this reduced the ember build portion of a ./launcher rebuild app from ~45 minutes to ~15 minutes.
There may also be a slight speed improvement for machines with more RAM, but nothing too substantial.
If you run Discourse on a low-memory machine, please give it a try and let us know how you get on!