Tobi Lütke's core methodology discipline. Systems design is the practice of thinking about businesses, products, and organizations as interconnected systems with feedback loops, constraints, and emergent behavior — rather than as static lists of features or headcount. Lütke talks about it as the most underrated skill in leadership: instead of solving one problem at a time, you redesign the system so the problem stops appearing. Directly applicable to FeatureOS's churn problem — which is a systems problem, not a feature problem.