Duolingo Software Engineer Interview Questions + Guide in 2025

Duolingo is on a mission to develop the best education in the world and make it universally available, leveraging innovative technology to enhance language learning for millions of users globally.

As a Software Engineer at Duolingo, you will play a crucial role in advancing the company's mission by developing cutting-edge software solutions that enhance user experiences. You will work on various projects that may span the full technology stack, focusing on building robust, scalable APIs and services that support Duolingo’s diverse product offerings. Key responsibilities include collaborating with product designers, engineers, and data scientists to implement features that are not only functional but also contribute to the overall educational goals of the platform. You will be expected to engage in code reviews, mentor junior engineers, and participate in the software development lifecycle from conception to deployment.

To excel in this role, you should possess strong competencies in data structures, algorithms, and software design principles. Experience with programming languages such as Java, Python, or Kotlin, and familiarity with cloud infrastructures and CI/CD practices will be essential. Additionally, successful candidates will demonstrate a problem-solving mindset, adaptability to new challenges, and effective communication skills to articulate technical concepts to both technical and non-technical stakeholders.

This guide aims to equip you with a deeper understanding of the expectations and interview processes at Duolingo, ultimately helping you to prepare effectively and confidently for your interview.

The interview process for a Software Engineer at Duolingo is structured and thorough, designed to assess both technical skills and cultural fit. The process typically consists of several distinct stages, each focusing on different competencies relevant to the role.

1. Initial Screening

The first step is an initial screening, usually conducted via a phone call with a recruiter. This conversation is an opportunity for the recruiter to understand your background, skills, and motivations for applying to Duolingo. They will also provide insights into the company culture and what to expect in the subsequent stages of the interview process.

2. Online Assessment

Following the initial screening, candidates are required to complete an online assessment. This assessment typically includes coding challenges that test your problem-solving abilities and understanding of algorithms and data structures. The questions may vary in difficulty and often reflect real-world scenarios you might encounter in the role.

3. Technical Interview

If you perform well in the online assessment, the next step is a technical interview, which may be conducted via video call. During this interview, you will be asked to solve coding problems in real-time, often using a collaborative coding platform. Interviewers may focus on your thought process, coding style, and ability to communicate your solutions effectively. Expect questions that require you to demonstrate your understanding of software design principles and your proficiency in programming languages relevant to the role, such as Python, Java, or Kotlin.

4. Onsite Interview

The final stage typically involves an onsite interview, which may be conducted virtually. This stage usually consists of multiple rounds, including technical interviews, pair programming exercises, and discussions with team members. You may be asked to work on a coding problem collaboratively, allowing interviewers to assess your teamwork and communication skills. Additionally, there may be behavioral interviews to evaluate your cultural fit within the company.

5. Final Evaluation

After the onsite interviews, candidates may have a final evaluation where they discuss their experiences and any projects they have worked on. This is also an opportunity for you to ask questions about the team, projects, and company culture.

As you prepare for your interview, be ready to tackle a variety of technical challenges and demonstrate your ability to work collaboratively. Next, let’s delve into the specific interview questions that candidates have encountered during the process.

Practice for the Duolingo Software Engineer interview with these recently asked interview questions.