It is relatively light on resources, you can even host it on your own PC. And it does not need to be public, just don't expose the port publicly and voila..
Ah thanks, I couldn't find anything about it. I run all my stuff on a server behind a Tailscale network, so nothing is accessible without VPN access. I thought it might need connections from other instances.
I just have whatever ports forwarded but I don't have signups public. It works fine except for the arm64 image not being updated but I switched to the other build of the docker image and it works.