Did the Chipotle online assessment and then the coding rounds in their full loop earlier this year. Writing this up because the OA format was unusual enough to be worth documenting.
The OA comes before the recruiter call, at least in the flow I went through. It was timed, 90 minutes, two coding problems and one shorter SQL/data question. Not a standard platform like HackerRank or Codility. It's hosted on their own internal assessment tool.
Problem difficulty: one easy-medium, one medium. Nothing I'd classify as hard. One was a string parsing problem. One was array manipulation with a few edge cases. The SQL question was a join with a filter. Definitely not trying to filter out people with LeetCode hard memorized.
What I noticed: they seemed more interested in clean, working code than in finding the optimal solution in 20 minutes. My solution to the second problem was not the most efficient approach and I still moved forward.
The in-loop coding rounds are harder. The phone screen was also two problems, one of which had a follow-up asking me to optimize the naive solution. The onsite coding round went into graph territory.
For context I have about 10 years of backend experience. I went in cold without grinding, cleared the OA fine, but I did need to brush up on some fundamentals for the deeper rounds.
A few things I'd tell someone prepping: Don't spend a week grinding mediums and hards just for the OA. It's not that kind of filter. Do be able to code cleanly and talk through your approach live. The live rounds care about that a lot. Brush up on trees/graphs for the onsite. At least one graph question seems common. SQL is genuinely tested. Not just "can you write a SELECT," actually joins and aggregations.
Happy to answer questions.