Duolingo · Metrics · Senior · 45 to 60 minutes

How should Duolingo break down DAU growth?

Duolingo is a consumer app and website that helps people learn languages for free, with a paid premium subscription for extra features. Answer this product management case and get it graded line by line against a weighted rubric.

Metric design
Product strategy
Prioritization
Experimentation
Cross functional communication

The situation

It is 2018. After several years of strong year over year growth, Duolingo's Daily Active Users have started to flatten. The company depends mostly on organic acquisition and a free product that later monetizes a small share of engaged learners, so leadership does not want to solve the problem by buying traffic. Product teams run many A/B tests, but the team responsible for growth says DAU is now too broad and slow moving to guide day to day decisions. Different teams argue for different focal metrics, such as new user retention, reactivation, streak behavior, or monthly actives, and there is no shared way to compare their impact on long term DAU. Your VP of Product and Head of Data Science ask you, a senior PM on growth, to propose a metric framework and prioritization approach for the next planning cycle. They need something specific enough to focus teams and forecast impact, but simple enough to explain across the organization. The hard part is choosing metrics that are both meaningful to the business and actually movable through experiments.

What to produce

Write a 1 to 2 page memo recommending Duolingo's growth metric framework and how to use it to prioritize the next 2 quarters of experimentation.

Your answer must

Define the north star metric and break it into 4 to 7 user lifecycle segments or transition metrics that roll up to it.
Explain why this framework is more actionable than using DAU alone, and how it covers acquisition, activation, retention, deactivation, and reactivation.
Describe a simple simulation, forecast, or sensitivity analysis that would let Duolingo compare which metric improvement is likely to create the most DAU growth over time.
Recommend which lever Duolingo should prioritize first, plus 1 to 2 guardrail metrics, and explain your reasoning.
List the key data and instrumentation needed to trust the framework, including how to avoid double counting users across devices or accounts.

Constraints

Do not assume a large increase in paid marketing spend, growth is primarily organic.
Tie every recommended metric back to DAU and long term learner value, not short term subscription revenue alone.
Keep the framework usable across many product teams and compatible with frequent A/B testing.

Format

A clear structure is Problem, Proposed metric tree or state model, Prioritization method, Recommendation, Risks and next steps.

How Duolingo actually played it

Duolingo's data science team explains the Growth Model, a framework of user states that helped grow DAUs 4 times since 2019. Simulating 2 percent monthly improvements in each transition showed that raising current user retention had the biggest impact on DAU. A standout example of a metric framework changing team focus.

Model user states to find the transition that matters most.
Simulate improvements to prioritize across teams.
As the base grows, retention dominates DAU growth.

Built from Meaningful metrics: How data sharpened the focus of product teams by Erin Gustafson.