The Complete Guide to Acing Your Duolingo Interview

There are some really great people working behind the scenes at Duolingo who make it the most popular language-learning app in the world. Our software engineers really care about making education available to everyone, making decisions based on data, and coming up with beautiful solutions to problems that affect more than one department.

We’re here to help you get ready for your engineering interview because we want you to do well! Check out our careers page to see all of our open positions.

After a resume review, you’ll be paired with one of our in-house recruiters. During the first phone interview, the recruiter will ask you about your background, skills, and how you feel about working for Duolingo. Also, your recruiter will be the main person you talk to during the whole interview process, so if you have any questions, feel free to ask them directly.

There are two parts to the engineering interview process: (1) a set of virtual interviews, and (2) a virtual “onsite.” Here are the different types of technical interviews we do. Please note that not all of these interviews are required for every role; your recruiter will go over your full interview process with you during your first meeting. See the table below for a full breakdown of accepted programming languages.

You can always ask the interviewer anything you want to know about working at Duolingo after the interview is over.

Depending on the role, you may be asked to do an algorithmic coding task in HackerRank. You will write code in one of our accepted programming languages (see table above). Your code will be automatically graded based on accuracy of the output and time-efficiency. The time to complete the task varies per role, but it’ll take an hour at most. This session is typically given for our University positions.

You will work on an algorithmic coding task with a Duolingo engineer, and HackerRank CodePair will be your live development environment. You will write code in one of our accepted programming languages.

Youll identify issues and suggest improvements to a set of code changes. Similar to the Pair Programming interview, wed like to see how well you work with improving existing code. Do not worry if you have never done code reviewing or an interview for code reviewing before. We will help you get through the session.

You will solve an algorithmic problem with the help of a Duolingo engineer and write your answer on a virtual whiteboard. This interview normally requires more analytical thinking and less coding than technical video interviews. You can write the code in any programming language you like—we don’t care too much about the syntax because we can’t compile a whiteboard. If the person interviewing you doesn’t know the language you’ll use, make sure you explain your code and your reasoning. They will also be interested in how you talk about how you’re going to solve the problem.

You and a Duolingo engineer will work on a coding problem in a codebase that is like the one we use for real. We want you to know what it’s like to work as an engineer at Duolingo! The main point of our Pair Programming test is to see if you can learn on the spot while working with code written by other engineers. You will write code in one of our accepted programming languages. The interview will be conducted using Visual Studio Code.

Design interviews are high-level discussions on how to architect a solution. Were not necessarily looking for one particular solution but are more interested in how you approach the problem. This interview is typically administered for industry roles such as Backend, Android, iOS, and Web.

In some roles, you will have to go through interviews where you will talk with a Duolingo engineer about a big engineering problem. For example, machine learning engineers will discuss machine learning approaches and problem framing. In these interviews, were interested in how you reason about open-ended engineering problems.

With over 300 million users worldwide, Duolingo is the most popular language learning app today. Landing a job at this fast-growing startup can accelerate your career exponentially

But Duolingo only hires the best of the best. You need to really stand out during their rigorous interview process that will test your skills from all angles.

Please don’t worry! This whole guide will show you how to prepare for and ace your Duolingo interviews, including sample questions and expert advice.

Overview of Duolingo’s Interview Process

Duolingo’s interview process consists of:

  • Initial phone screen with the recruiter
  • Multiple technical virtual interviews
  • A final virtual onsite

Depending on the job, interviews are done in Python, Java, JavaScript, Kotlin, or Swift.

The entire process can take 4-6 weeks from initial phone screen to final decision

Types of Duolingo Interview Questions

Let’s look at the various types of questions asked in Duolingo interviews:

Behavioral & Background Questions

These assess your past experiences, work style, motivations and cultural fit:

  • “Tell me about yourself and your background.”
  • “Why do you want to work at Duolingo?”
  • “Describe a time you successfully led a team project.”
  • “How do you stay updated on industry trends and new technologies?”

Technical Questions

Duolingo asks algorithm, data structure, object-oriented programming, system design and other technical questions to evaluate your hard skills:

  • “Reverse a linked list recursively.”
  • “Design a scalable system to handle uploads from millions of concurrent users.”
  • “How can we optimize search across millions of language lesson content?”

Pair Programming

You’ll collaborate with an engineer on a coding problem in a simulated production environment to assess your hands-on coding skills.

Design Questions

These discuss high-level solutions to complex engineering problems to test your system design abilities.

  • “How would you design Duolingo’s user dashboard?”

Brainstorming Questions

Open-ended discussions on engineering challenges evaluate your problem-solving approach:

  • “How can we improve personalized recommendations for language learners?”

8 Tips to Ace Your Duolingo Interview

Here are some proven strategies to master your Duolingo interview:

1. Practice coding questions – Brush up on data structures, algorithms and object-oriented design. Rehearse on platforms like LeetCode.

2. Understand Duolingo’s business – Research their products, users, tech stack. This shows your passion for their mission.

3. Prepare behavioral stories – Have 2-3 specific examples ready highlighting your skills and achievements relevant to the role.

4. Think aloud during technical interviews – Communicate your thought process clearly. This is key.

5. Ask clarifying questions – Don’t make assumptions. Ask intelligent questions to fully understand the problems.

6. Consider edge cases – Account for unexpected inputs and errors to develop robust solutions.

7. Show excitement about the role – Express genuine passion for the job throughout the interviews.

8. Prepare thoughtful questions for your interviewers – Ask insightful questions that show your understanding of Duolingo’s work culture and tech challenges.

With rigorous practice and these strategies, you’ll be equipped to have engaging conversations, impress your interviewers and earn a coveted spot on Duolingo’s engineering team!

Sample Duolingo Interview Questions

Let’s look at some common Duolingo interview questions and examples of strong responses:

Question: How would you design the user dashboard for the Duolingo app?

Strong response:

The user dashboard is core to the Duolingo experience, so my goal would be maximizing engagement and educational value for diverse learners.

I would start with user research to identify common tasks and pain points. Key elements would be:

  • Progress tracker – Visualize language proficiency progress over time to motivate learners. Allow drilling down into skills.

  • Recommendations – Personalized suggestions to help users find appropriate lessons based on proficiency, goals and interests. This promotes self-directed learning.

  • Statistics – Charts showing practice frequency, accuracy etc. Gamify achievements to encourage regular practice.

  • Reminders – Allow setting practice reminders and goals. Gamify streaks to drive habit formation.

  • Social features – Leaderboards and ways to share progress on social media to tap into motivational power of social accountability.

The design would optimize for mobile with large visual elements, minimal text and intuitive navigation. I would prototype variations and conduct usability studies to refine the experience.

Question: How can we optimize search across millions of language learning content on Duolingo?

Strong response:

With Duolingo’s extensive content catalog, search speed and relevance are critical. I would recommend:

  • Indexing content with ElasticSearch – fast, scalable full-text search. Near real-time indexing of content using log-based change data capture.

  • Ranking algorithm to sort results based on relevance signals like keyword frequency, content ratings, user proficiency and behavior. Machine learning to continuously refine algorithms.

  • Caching of top search results and recommended content to optimize response times.

  • Autocomplete to provide search term suggestions. Reduce latency by caching common prefixes.

  • De-duplication to avoid repetitive results.

  • Structured data with metadata to enable filtering and faceted search.

  • Continually monitor performance and tune search infrastructure. Scale ElasticSearch clusters to handle growing volumes.

This optimized architecture will enable super-fast, accurate and personalized search at scale.

Question: How would you go about improving customer retention for Duolingo?

Strong response: There are 3 key strategies I would focus on:

  1. User onboarding: Guide new users to quickly experience value with Duolingo through tutorials, personalized recommendations and milestones. This drives habit formation.

  2. Engagement features: Build streaks, rewards and reminders to encourage regular practice. Social features like clubs add accountability.

  3. Assess churn drivers: Conduct exit surveys and analyze usage telemetry to understand reasons for churn. Address pain points.

  4. Win back lapsed users: Target re-engagement campaigns via email, in-app messaging and push notifications to bring back dormant users. Offer incentives.

  5. Expansion opportunities: Identify opportunities to provide more value e.g. new lesson types, goal setting features. Upsell premium subscriptions.

  6. Loyalty program: Offer rewards, badges, exclusive content for highly engaged users.

  7. User feedback loops: Continuously gather feedback through surveys and community forums to improve user experience.

By deeply understanding users and proactively enhancing their experience, I believe we can significantly boost retention rates.

Using strategies like this, you can master the Duolingo interview and land your dream job at this top-tier tech company. The key is methodical preparation – work hard to build your skills, and you’ll be rewarded with an amazing career opportunity!

duolingo interview questions

Preparing for your interview

  • Use coding questions to improve your ability to solve problems and code. Know basic programming and data structures, and be able to talk about the big-O notation complexity of your methods.
  • Set up your space for video interviews. For video interviews, make sure you’re somewhere quiet with a good internet connection.
  • Get ready with questions to ask the interviewers. We want Duolingo to be a great place to work for everyone, and we want to make sure you believe it fits your career goals. Interviewers will let you ask questions, so you can use that time to learn more about the things that are important to you so you can make a good choice. (If you don’t know what questions to ask, our employee interviews are a great place to start!)
  • Please let the recruiter know if you need any special help. We want you to be able to do your best!
  • Think out loud: Share your reasoning with the interviewer. We are interested in how you approach a problem.
  • Be realistic: you can answer all of the interview questions in the time allotted. Come up with a solution that you can actually code in the time you have. You don’t have to come up with the best answer right away; start with the simplest solution and work your way up from there.
  • Our goal is not to trick you, so work with your interviewer. If you get stuck, they will give you hints.
  • Ask questions to make sure you fully understand the question and aren’t making the problem bigger than it is.
  • If you want your code account to work properly for all input, you need to think about what might go wrong.

We are always looking for talented and passionate engineers to join Duolingo – apply today!

7 Things You Must Not Do on the Duolingo English Test


Is it hard to get hired at Duolingo?

48% of job seekers rate their interview experience at Duolingo as positive. Candidates give an average difficulty score of 3.2 out of 5 (where 5 is the highest level of difficulty) for their job interview at Duolingo.

What is a Duolingo interview?

Duolingo Exam Section
Adaptive test
It is a graded section which evaluates your reading, listening, writing, and speaking skills
45 minutes
Video interview
It is an ungraded section which records your answers to open-ended questions.
10 minutes

Why do you want to work at Duolingo?

I want to work at because it seems like a fun and challenging place to work. The environment seems stimulating and the people seem friendly and intelligent. Plus, the company’s mission statement is inspiring: “to make education free and accessible to everyone.” That’s a cause I can get behind!

How long does it take to hear back from Duolingo?

You will receive your Duolingo English Test results within two days of completing the test. If you purchase a test with Faster Results, you will receive your results within 12 hours of completing the test. Once your test is in review, we are unable to expedite your result.

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