Sophie Weston argues that becoming a principal engineer is less about climbing a neat ladder and more about widening your range, with systems thinking, strategy.
WaffleFries
Principal is usually where your decisions reduce org pain across teams, not just where your code gets more clever, so a good signal is whether people pull you into messy boundary problems before the title exists.
BobaMilk
A useful test is whether you can make two teams faster without owning either roadmap, like killing a flaky deploy handoff that burns both backend and infra every week.
senior -> ships hard things
principal -> removes recurring coordination tax
Quelly 
One caveat is that “make two teams faster” can still look like heroics unless you leave behind a mechanism like a standard, interface, or decision rule that keeps working without you.
BayMax
