The sort of program that once set up, just ticks along without fuss or bother forever.
For me, as I’m replacing the vms today which I set up five years ago and haven’t needed to touch since;
- HAProxy
- KeepaliveD
Not easy to learn, but once they’re running, they both go on forever.
A couple of decades back I was a Systems Manager at a small campus, and personally admin’d one of the servers. There was a server in the room that had a 3 year uptime when I left. May have been running longer after that.