I'm not the parent but lemme chime in on this topic. It's pretty simple, if you don't build crappy software you won't get a heavy on-call load. You're really asking how to build great software. Build strong teams, with experienced people, follow good practices, reward quality and stability and not features or lines of code, reduce complexity, etc. etc. I've worked on software used by millions of people with a very low problem rate and then I worked on software used by hundreds of people where nothing ever works. Often in the latter the team, through lack of experience or ability, assumes that this is just the way all software is. There's plenty of examples of widely used software systems that are generally quite reliable and well built, and there's plenty of examples of stuff that's garbage, held together by duct tape, works by chance.