Product design question

Design a subway system.

Practice this question out loud. An AI interviewer asks it, follows up like a real interviewer would, and scores your answer. Type or speak.

What this question tests

Tests structured product and systems design for physical infrastructure, forcing prioritization of routes and capacity under real constraints.

Clarify scope: a new subway system for a specific city, and confirm assumed density with the interviewer.
Identify core requirements: connect dense residential areas to major employment hubs first, since ridership justifies cost.
Prioritize route planning using demand data: commute patterns or existing transit ridership as a proxy.
Design for capacity: peak-hour train frequency and platform sizing based on expected peak demand, with redundancy.
Address accessibility: step-free access at every station as a baseline requirement, not an afterthought.
Define success as ridership relative to projected demand and on-time performance, not just miles of track.

Prioritizes routes using an explicit demand signal, commute patterns, rather than an arbitrary layout.
Treats accessibility as a baseline requirement, reflecting real transit design standards.
Picks success metrics reflecting actual usability, not just physical scale.

Chapters of the AI PM course that teach what this question tests.