The last 3 companies I've worked for had no juniors and mid-levels, but only seniors and a handful or staff engineers. What staff engineers did on a day-to-day basis was hardly different from what the senior engineers do, besides having more responsibilities and maybe more say over things like architecture. Depending on the company, a staff engineer could be managing or not managing at all. In general, I don't think these title really mean a whole lot, that is unless one is intent on managing specifically.
The last 3 companies I've worked for had no juniors and mid-levels, but only seniors and a handful or staff engineers. What staff engineers did on a day-to-day basis was hardly different from what the senior engineers do, besides having more responsibilities and maybe more say over things like architecture. Depending on the company, a staff engineer could be managing or not managing at all. In general, I don't think these title really mean a whole lot, that is unless one is intent on managing specifically.