Duolingo · Metrics · Senior · 45 to 60 minutes

Which growth lever should Duolingo back?

Duolingo is a mobile and web app that helps people learn languages through short, gamified lessons. Answer this product management case and get it graded line by line against a weighted rubric.

Metrics strategy
Growth modeling
Prioritization
Experiment design
Executive communication

The situation

It is late 2018. Duolingo is already the most downloaded education app in the world, but daily active user growth has slowed to single digits year over year. The company still gets most new users organically, investors expect stronger growth, and the team has just come off two weak bets: an added lesson mechanic inspired by a popular mobile game did not improve retention, and a referral program lifted new users only slightly. The Head of Product asks you, a senior PM in growth, to recommend what the company should optimize next and how to decide with data, before another quarter is spent on the wrong bet. Assume you have access to historical daily user activity, experiment results, and the ability to form one small cross functional team. The hard part is that several levers look plausible, acquisition, new user onboarding, reactivation, retention, notifications, and gamification, but there is no shared model for which one would matter most to DAU. Your job is not to pitch a single feature. It is to define the metric framework, choose the highest leverage product problem, and outline the first experiments while protecting learner trust and the learning experience.

What to produce

A 2 page strategy memo.

Your answer must

State the primary business goal for the next 12 months and choose one north star metric to optimize, with a brief explanation of why DAU, WAU, and MAU are not interchangeable here.
Propose a user engagement model that partitions the user base into clear, non overlapping states and names the key transition rates you would track between them.
Compare at least three plausible growth levers, such as new user acquisition, new user retention, current user retention, and reactivation, and rank them by likely impact on DAU and difficulty to move.
Recommend the first two product or experiment areas to pursue, and explain why they fit Duolingo's context better than simply copying tactics from another app.
List the main risks, guardrails, and success checks, including learner trust, notification fatigue, and unintended harm to the learning experience or monetization.

Constraints

Do not assume a new paid marketing budget, most acquisition remains organic.
You can create only one small cross functional team for the next two quarters.
Use metrics that can be measured from existing daily product data and normal experiment tooling.
Do not rely on changes that make lessons materially worse just to boost short term engagement.

Format

Use brief headings, one simple user state table, and one prioritization table.

How Duolingo actually played it

Duolingo's former product chief explains how a user segment model showed that retaining current users mattered most. That finding led to leagues, careful notifications and streak upgrades that multiplied daily active users.

A simple growth model can tell you which lever to pull
Make the lever your north star for the team
Test notification volume so you do not burn trust

Built from How Duolingo reignited user growth by Jorge Mazal (Lenny's Newsletter).