How would you tell whether a new product has product-market fit?
What the interviewer wants to hear
- Retention curves that flatten
- Sean Ellis survey: share very disappointed without it
- Organic growth, referrals and word of mouth
- Strong engagement and willingness to pay
- Qualitative signs: customers pull the product
Model answer
I look at behaviour first. The strongest signal is retention: cohort curves that drop and then flatten, showing a group of users who keep getting value, ideally with newer cohorts flattening higher. I also run the Sean Ellis survey asking how users would feel if they could no longer use the product; around 40% or more saying "very disappointed" is a common benchmark. Then I look for organic pull: growth from referrals and word of mouth, not only paid acquisition, and customers who pay without heavy discounts and renew. Qualitatively, fit feels like demand pulling the product: customers ask for more, complain loudly when it breaks and recommend it. I usually find fit is strong in one segment first, so I analyse these signals by segment and focus on where they are strongest.
Can you answer it under time pressure?
Take a timed medium round and get scored on every answer.
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