Cognitiv Software Engineer Interview Experience — High-Bar Technical Screen, Rejected Over Spark and C#

Cognitiv is a small startup that works with ads data. They were opening a new office in Canada, so they were hiring.

After the recruiter interview, the first round was scheduled with the hiring manager. They asked BQ questions along with technical experience questions related to what the team needed — things like how to handle data duplication, Spark-related questions, how to scale data... If you don't have real experience with this stuff, you basically can't answer well. I don't have Spark experience, and the HM could tell right away — they said "I can tell you haven't used Spark..." But overall the interview felt okay.

The next round was a technical screen, one hour, one-on-one with a staff engineer on the team. Before the interview the recruiter had already said the bar would be pretty high, since this is a founding member role.

The technical interview had two questions: given a library system setup, write a SQL query to filter books — basically joining five tables. I did this one well, but it took a while (I focused on demonstrating communication rather than pushing myself to go fast). The second was a variant of an old LeetCode problem, basically a hard-level DP grid type. They didn't ask for the optimal solution — with time very limited, they just wanted a brute-force solution. But I got a bit flustered, and even the brute force wasn't written well — I missed a few edge cases.

The day after the technical interview I got an email saying that after further consideration, they'd found a more suitable candidate.

My guess is the reasons were: the company mainly uses C# and I only know Python, not a compiled language (the interviewer specifically asked whether I knew C#); I don't know Spark, so the HM probably felt that instead of betting on me learning it quickly, it made more sense to go with someone who already had years of experience; and the technical interview itself didn't go that well.

Overall the interview process felt pretty good — everyone was polite, and communication was friendly.