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VerifiedUnited StatesOnsite2 months ago
Sierra AI

Agent Engineer Interview Experience

Sierra AI
I told Sierra I’d only worked in Python, they said that was fine, and then my first onsite was a TypeScript React debugging round where the interviewer showed up 10 or 15 minutes late and was super rude and cold.
Result
Rejected
Interview date
a year ago
Timespan
6 weeks
Difficulty
Difficult

Interview process

I got in through a referral, and the process was a recruiter screen, one LeetCode-style technical screen, then an onsite that included a take-home plus three 1-hour rounds. For a startup, it felt weirdly mature and standardized, more like big tech: everyone I met was in the agent engineering org, the recruiter was polished, and they were even fine with me pushing the coding screen out by over a month. The phone screen was a pretty standard cycle-detection problem dressed up as an Excel question, and then the take-home was much more job-relevant because I had to build a small customer support agent and think about prioritization, metrics, and observability. Most of the loop felt friendly and professional, but the big gotcha was a TypeScript and React debugging round that they framed as conceptual even though I think you really do need to know that stack to pass it. I didn't get the offer, and honestly I think that debugging round was the reason because the rest of the process felt solid.

  • Recruiter screen
  • Technical interview
  • Take-home project
  • Final round

Interview tips

I'd prep this in two separate lanes. First, do the normal graph and tree LeetCode prep because the phone screen was basically that. Second, do not believe the language-agnostic framing for the onsite debugging round. If you're interviewing here, I would absolutely get comfortable with TypeScript and basic React. For the take-home, practice building a simple agent without hiding behind a big framework, understand OpenAI tool calling, and be ready to talk through metrics, observability, and why you chose what to ship. Also, if I could do it over, I would avoid getting boxed into a comp range on the first recruiter call. It seems like Sierra was hiring very aggressively and had already built a very repeatable process around that. When I was onsite, basically every conference room had interviews going on, and I'm pretty sure they were asking the same technical screen question to everyone. It felt org-dependent rather than team-random, and every single person I met was an agent engineer, not a bunch of cross-functional interviewers.

Company culture

Compared with other AI startups I talked to, Sierra felt much more professional and recruiter-driven in a big-tech way, even though I did run into one clearly rogue interviewer. The role also felt a little forward-deployed-engineer-ish to me, with a lot of customer implementation energy, probably more post-sales than pre-sales, and I noticed they seemed to like engineering profiles that also had a business lens.

Questions asked

Overview

This was a TypeScript and React debugging round that I think was the real gate, and for me it was easily the worst part of the process because it was not actually language-agnostic and the main interviewer was cold.

Question types asked

Specific questions asked

Here's some prewritten TypeScript and React code with several bugs in it. Can you debug and fix it?

I had already told them I was basically a Python person and had asked if I could do this round in Python, but they said no. I spent about a week trying to learn enough TypeScript and React to survive it and still felt behind. The interview started 10 to 15 minutes late, there were two interviewers, and the main one was rude and very critical from the start. There were around five or six things to debug, and even if you know the stack it's a time crunch. I pretty much bombed this round.

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