Product design question
Design a mobile app that allows users to easily buy and sell used books.
- Product design
- Easy
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What this question tests
Tests product design for a peer-to-peer marketplace with a specific, niche item category (used books) that has unique condition and pricing challenges.
How to approach it
- Identify the target user: students and casual readers wanting to save money and reduce waste, versus rare-book collectors, prioritizing the larger, simpler student segment first.
- Identify the core pain point: pricing a used book fairly is hard for a casual seller, and buyers worry about condition accuracy (highlighting, missing pages).
- Design around pricing: an ISBN-scan-based pricing suggestion tool comparing to recent sold listings, reducing seller friction and buyer price anxiety.
- Design around condition trust: a standardized condition rating scale (like new, good, acceptable) with required photo evidence for anything below 'like new'.
- Define success: listing-to-sale conversion rate and post-sale dispute rate, since both measure whether the pricing and trust mechanisms actually work.
What a strong answer includes
- Identifies pricing uncertainty and condition trust as the two real, specific frictions in used-book resale, rather than generic marketplace features.
- Proposes ISBN-based automated pricing suggestions, a concrete, technically feasible mechanism that directly reduces seller effort and buyer risk.
- Uses an illustrative number, e.g. assume 40% of casual sellers never list because pricing feels too hard, motivating the pricing-assist feature.
- Picks conversion and dispute rate as success metrics, tying directly back to the specific problems identified.
Common mistakes
- Designing a generic e-commerce marketplace without addressing the specific pricing and condition-trust challenges of used books.
- Ignoring the ISBN-based standardization opportunity that makes book pricing and cataloging easier than most other used-goods categories.
Likely follow-up questions
- How would you handle textbook edition mismatches, a common source of buyer disputes?
- How would you monetize this marketplace without discouraging student sellers with thin margins?
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Learn the skill behind it
Chapters of the AI PM course that teach what this question tests.
- Chapter 4: Discovery and strategy for AI products
- Chapter 7: AI UX and human oversight: design for a system that is wrong sometimes
- Chapter 14: Get the job: the AI PM interview loop