Arista Software Engineer Interview Experience — Rejected After Solving Both Problems Optimally

Arista·Software Engineer·Feb 2026
Technical ScreenRejectedeasy

There were two questions total: one palindrome string problem, one missing number problem. After I finished each one, they asked me for the time and space complexity. There were no resume questions, no other questions, not even a self-introduction.

Overall the questions weren't hard. For the palindrome one, I considered the case where the string is "", but I didn't consider the case where it's directly null, and I got stuck for a bit there. Their coding system (coderpad) was kind of mysterious too — it's not the core LeetCode-style mode, and I was confused by the error message for a while before the interviewer gave me a hint and I got it working.

Then the second question, missing number, was a variant of the original LeetCode problem — it doesn't start from 0. I first wrote the Gauss's formula math approach (O(n) complexity), then wrote the binary search optimization (I figured binary search was expected, O(log n) complexity). The two questions took about 40 minutes total.

A few days later I got the rejection letter. I emailed asking for feedback, and they said they wanted me to be more fluent at reading errors and debugging.

All I can say is the bar is pretty high now — I wrote the optimal solution and the interviewer still found something to pick at, gave me more hints than they'd like to. You only really understand this once you've done enough problems and spent enough time on it.

Later I talked to the guy who referred me. He said a friend he'd referred before finished all the questions in the second round in half an hour, but still got rejected — because they wanted it done in twenty minutes.

There's no way around it at this point. Why even bother testing LeetCode then, just memorize everything cold. It feels like the interviewer doesn't want to see your thinking process at all, they just want to see you look at the question and instantly recite the optimal solution from memory, and whoever takes less time gets in.

Published

Curated and edited by PracHub

Practice the questions from this interview

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Interview at a glance

Company
Arista
Role
Software Engineer
Rounds
Technical Screen
Outcome
Rejected
Difficulty
easy
Interview date
Feb 2026
Questions from this interview
1 question

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