It's worth mentioning that the level of "principal engineer" means different things at different companies. Some companies have "principal" and "sr. principal"

It's worth mentioning that the level of "principal engineer" means different things at different companies. Some companies have "principal" and "sr. principal" while others have "staff" and "principal". See www.levels.fyi for a rough alignment guide. Regardless of what they are called, the different levels almost always involve changes in job function, not just "more of the same". This is true even in the distinction between "software engineer" and "senior software engineer", where the latter typically involves a lot more consulting, mentoring, and review and less writing code.