I worked with a guy who seemingly intentionally engineered his “bus factor” down to one. He worked on a giant inscrutable shell script that was used in all our provisioning, and it was kept solely on his laptop in RCS (https://www.gnu.org/software/rcs/)

So obviously, additions or changes all had to go through him. I’ve never seen such aggressive gatekeeping before or since. I’m still a little impressed!

It's a subtle art that doesn't get as much attention as it should. Instead everybody is into design patterns and functional programming and all that garbage.

Fortunately masters in this art have codified it's techniques in this classic tome: https://github.com/Droogans/unmaintainable-code