How would you measure product success?

You are interviewing for a Data Scientist role supporting a subscription-based collaborative design software product used by teams. The product is sold primarily through seat-based subscriptions to companies, so the economic buyer and the day-to-day end user may be different. The hiring manager asks: 1. How would you measure this product's success? 2. What north-star, input, and guardrail metrics would you use? 3. How would you define power users in a way that is useful for product and business decisions? Your answer should discuss the appropriate unit of analysis such as user, team, workspace, or account; tradeoffs between engagement, collaboration, monetization, and retention metrics; and how you would validate that your power-user definition is meaningful rather than arbitrary.