How Duolingo Built Duolingo Max

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Apr 16, 2025

Natalia Castillejo, Director of Product at Duolingo, has been instrumental in the development of innovative features like Duolingo Max. She shares insights on how AI-driven functionalities like video calls and personalized feedback revolutionized language learning. Discussing her journey from intern to director, Natalia highlights the importance of user-centric design and A/B testing in product development. She emphasizes that successful monetization requires understanding user needs, paving the way for engaging educational experiences.

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INSIGHT

AI Unlocks Personalized Learning

Early access to ChatGPT enabled Duolingo to create highly personalized language learning features.
AI unlocked possibilities like personalized feedback on errors and dynamic conversations that were previously impossible.

ADVICE

Start With User Needs

Begin product development by identifying users' real needs, not technology capabilities.
Focus on making AI conversations feel natural and friends-like to boost engagement.

ANECDOTE

Simplified AI Feedback Boosted Usage

Initial AI-based Explain My Answer was a chatbot requiring users to ask questions, which was too demanding.
Simplifying it to direct feedback increased usage and user satisfaction.

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Natalia Castillejo is a Director of Product at Duolingo, where she has spent the last decade since graduating from Yale University in 2016. Natalia started her PM career at Duolingo working on the company’s English Language Test and other core product features. More recently, she helped lead the development and monetization of AI-powered features like “Video Call,” “Roleplay,” and “Explain My Answer” that form the core of Duolingo Max, and then transitioned from core product to monetization to help accelerate the growth of this new higher-priced subscription tier.

Key Takeaways:

Duolingo started investing in AI product features in 2022 after getting early access to ChatGPT. It spent a year building and refining these features before packaging them into its new higher-priced Duolingo Max subscription tier in 2023.
Duolingo Max wasn’t an overnight success. It wasn’t until the company launched video calls and repositioned Max from “pay more for AI” to “pay more for conversational language learning” that the new subscription tier really took off.
Duolingo requires all PMs to be daily users of its app, and the company A/B tests every product change. This has led to a world-class product development culture built on both strong product intuition and rigorous experimentation.
Duolingo always starts with the user problem that needs to be solved and works backward from there. This helps avoid “technology in search of a problem,” which is especially important right now as AI is unlocking all sorts of new technology.
Duolingo is also encouraging its PMs to invest in AI tools to boost efficiency. This includes using tools like Replit to build prototypes without engineers, and building internal tools to predict the impact of an A/B test based on previous experiments.

Natalia Castillejo:

LinkedIn: https://www.linkedin.com/in/natic/
X: https://x.com/naticsti

Phil’s Carter:

Website: https://www.philgcarter.com
Substack: https://philgcarter.substack.com
LinkedIn: https://www.linkedin.com/in/philgcarter
X: https://x.com/philgcarter

Podcast Production by Podders: https://podders.io