Duolingo Software Engineer Interview Guide

Candidates report an initial recruiter call covering background, reason for job searching, salary expectations, and an overview of the process ahead. This stage is typically described as straightforward.

Depending on the role, this stage may be a CodeSignal or Karat assessment, a HackerRank screen, or a live phone-screen coding problem. Candidates report LeetCode-style medium problems covering trees, graphs, dynamic programming, and arrays. These often come with follow-up questions about optimizing the solution or explaining time and space complexity out loud.

Multiple candidates describe a pair programming round that is less about reciting algorithms and more about working through a problem together. In one case, the candidate debugged code from Duolingo's actual codebase. Interviewers reportedly valued clear communication, clarifying questions, and narrated reasoning over arriving at one perfect answer.

Several candidates were asked to review a pull request for quality issues, bugs, or best-practice concerns rather than write code from scratch. One candidate's review involved an infrastructure-as-code pull request, which required some familiarity with IaC patterns beyond general programming ability.

Some loops include a hard system or technical design round focused on architectural trade-offs and the ability to reason through decisions clearly. Interviewers reportedly care more about the thinking process than about landing on one specific design.

The loop typically closes with a behavioral or hiring-manager conversation about team fit, motivation for joining Duolingo, and working style. One candidate described this final chat as ungraded, while others treated it as a standard culture-fit discussion.