Focus on adoption challenges, not just the components you created. A design system nobody uses is not a design system.
Look for understanding of: component taxonomy, design tokens, documentation, governance, adoption strategy, and engineering collaboration. Best candidates discuss the challenge of balancing consistency with flexibility, and getting team buy-in. They should mention versioning and maintenance.
Reveals systems thinking and collaboration skills. Senior designers should be able to discuss governance, versioning, and scaling a design system across teams.