Citadel Software Engineer Interview Experience — A Maddeningly Vague Data Sampling Question

Citadel·Software Engineer·Aug 2026
Technical Screenmedium

Citadel is out of their minds.

The first half was fine — a normal self-introduction, project walkthrough, basic behavioral questions.

Then the coding part started and that's where the craziness began:

The interviewer was mumbling and couldn't speak clearly, and gave me a purely verbal problem: "we have millions of data points that need to be labeled," and told me to find the useful data. I kept following up, and he finally said "get 200 out of 1 million data points." I asked "what counts as useful data," and the interviewer wouldn't say. I asked how he wanted me to sample, and he wouldn't say that either.

OK fine, I proposed random sampling — he said that works but isn't optimal. I brought up least recently used, most frequently used, average, median, p99, p75, that kind of thing — he said it can only be called once. I followed up again asking "do I need to assume an object and then come up with several useful features" — he said he didn't know what features even meant.

Can someone please tell me what on earth this company, and this question, actually WANT! TO! DO!!!!!!

Published

Curated and edited by PracHub

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Interview at a glance

Company
Citadel
Role
Software Engineer
Rounds
Technical Screen
Difficulty
medium
Interview date
Aug 2026
Questions from this interview
1 question

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