450 people and growing 40% a year: are six levels enough, or are we storing up trouble?

Before adding levels, look at whether your level 3 is one job or two. If the nine-year people are doing visibly different work, split it. If they are doing the same work for longer, a new level just gives you a tenure step with a title, and you will have the same complaint at the new boundary in three years.

I went through this at a payments company that grew from 500 to 1,800. What I would do in your position: design for nine levels on the individual track, populate seven now, and split only your current level 3, into two levels with criteria that differ on scope and independence, not years.

Everyone else keeps their position relative to their peers, so it reads as one level being divided, not a re-grade.

Budget for the split, though. About 30% of our old level 3 landed in the upper half, and their pay needed a 4 to 6% correction to sit sensibly in the new range.

Really helpful, thank you. I checked this afternoon and the work at level 3 does differ: the longer-serving people are leading workstreams without supervision. So a split is justified on the work. I'll design for nine, populate seven, and cost the correction before I take it to the founders.