← Instacart Interview Insights
This is the kind of question where saying 'randomize users to treatment and control' is basically the wrong answer and they're waiting for you to realize that.
Start by acknowledging the two-sided nature of the marketplace and the potential for interference between treatment and control groups. Propose a cluster-based randomization (e.g., by geography or time) to minimize spillover, and define clear metrics for both sides (e.g., shopper participation, ETA, order volume). Outline a phased approach: pilot, measure, iterate, and scale if successful.
Pro tip: Emphasize the importance of monitoring guardrail metrics (e.g., overall marketplace health, customer satisfaction) to detect unintended consequences early. Consider using switchback or time-based randomization to account for temporal dynamics in supply and demand.
Clearly state the goal: shift shopper behavior to rush hours. Formulate hypotheses about how pricing changes will affect both shoppers and customers, including potential trade-offs.
Select a randomization unit that minimizes interference, such as geographic clusters, time slots (switchback), or shopper cohorts. Avoid individual-level randomization if spillover is likely.
Define primary metrics (e.g., % of orders in rush hours, shopper earnings) and guardrail metrics (e.g., overall delivery time, customer satisfaction, cancellation rates) to monitor marketplace health.
Implement the experiment with appropriate sample size and duration. Consider a phased rollout: pilot in a small region, then expand if results are promising and guardrails are not violated.
Analyze results using appropriate statistical methods (e.g., difference-in-differences, CUPED) to account for interference. If successful, iterate on pricing parameters; if not, diagnose and refine.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.