Interview format

Core Expertise

The Core Expertise interview tests a candidate’s mastery over a core technical discipline.

We administer the Core Expertise interview to early-career candidates who have not yet worked closely on large-scale production software systems. In these cases, a System Design interview provides very noisy signal due to the candidate’s lack of practical exposure to the concepts tested. Therefore, we instead test for technical depth on the candidate’s “home turf” (i.e., a technical discipline chosen by the candidate).

Procedure

If you’re administered a Core Expertise interview, here’s what you can expect:

Before the interview: you’ll be presented with at least four choices of disciplines, typically drawn from computer science and applied mathematics. You’ll confirm your choice of discipline with your recruiter.

During the interview: you’ll work through multiple problems in your chosen discipline with your interviewer. These problems will vary in length and complexity, allowing you to showcase your depth of knowledge and command over your chosen discipline. You’ll have access to a physical or virtual whiteboard, depending on the interview setting.

Evaluation criteria

There’s no strict rubric for a Core Expertise round, and there’s no magic number of questions that must be solved for a positive evaluation. Ultimately, the interviewer wants to understand your technical depth, the rigor of your thinking, and the clarity of your solution approaches.

Tips

Here are some tips for success on the Core Expertise interview:

• You should choose a discipline based on your own strengths, not what you perceive is most important to Perplexity. We don’t use the Core Expertise interview for team/project assignment.
• If a particular question is so alien that you don’t know where to start, it’s 100% OK to say “I don’t know” and move on. Doing this is preferable to spending 10 minutes guessing in the dark.
• At the same time, many questions will require some deep thinking to solve. It’s OK to take a minute or two to gather your thoughts before starting to solve a problem.
• Asking clarifying questions is welcome (and, in some cases, necessary to produce a sound solution).