There are two types of bus factors though. It’s true that at a small company, you can’t share all your responsibilities with someone else, but you can make sure

There are two types of bus factors though. It’s true that at a small company, you can’t share all your responsibilities with someone else, but you can make sure that if they need to you can be replaced by someone else (ie. if you get hit by a bus) by doing things like documenting your work. Alternatively, if you want to make sure your job is secure, don’t do that, but make sure you’re doing it knowingly.