Duolingo · Product sense · Entry · 45 to 60 minutes

How should Duolingo test demand?

Duolingo is a consumer app that helps people learn languages on their phones. Answer this product management case and get it graded line by line against a weighted rubric.

Product sense
Experiment design
User research
Prioritization
Metrics

The situation

Duolingo is still an idea, not yet a finished product. Luis von Ahn and Severin Hacker believe free language learning on a phone could reach a huge audience, but they have not built lessons, an app, or a large team. They ask you, a product minded early hire, for a plan to answer one question before they invest more time and money: do enough people care enough to take action? The challenge is that language learning sounds broadly appealing in conversation, so simple surveys or friendly opinions may overstate demand. At the same time, the team also needs to learn who is most interested and why, because the first version cannot serve every learner equally well. You need a fast, low cost way to test real interest, gather useful signals about potential users, and avoid overbuilding before the basics are proven. Your recommendation should help the founders decide whether to move forward, what evidence would count as validation, and what they should learn from the earliest people who show interest.

What to produce

Write a 1 page product brief, 500 to 700 words.

Your answer must

State the decision to be made and the main uncertainty your plan will reduce.
Identify 1 to 2 target user groups or core use cases to investigate first.
Propose a low cost validation plan with a clear sequence of steps and why each step is included.
Define the behavioral signals and metrics you would track, plus the threshold or decision rule for moving forward, iterating, or stopping.
Describe how you would learn from the earliest interested users and how that learning would shape the first product scope.
Call out the main risks in your approach and how you would handle interest from people before the product is ready.

Constraints

You cannot build a full mobile app or lesson system for this test.
Budget and headcount are very limited.
The founders need an answer within a few weeks.
Stated survey interest alone is not enough evidence of demand.

Format

Use short sections titled goal, target users, validation plan, metrics, user learning, and risks.

How Duolingo actually played it

Describes how Duolingo tested demand with a landing page and early signups before building, and how behavior and user conversations guided it.

Validate demand before building
Watch behavior over opinions
Talk to the earliest signups

Built from Duolingo's Quiet Test: how they validated demand before building by Sreerag Panat.