Just finished the Box coding round as part of a senior SWE loop, wanted to write up what the format actually looked like since I couldn't find a clear answer when I was prepping.
The online assessment came first, before any recruiter screen. Two coding problems, 90 minutes, HackerRank platform. The difficulty felt closer to LeetCode medium than hard. One was a string manipulation problem, one was more graph-adjacent but nothing extreme. The constraints were relaxed enough that a clean O(n log n) or even O(n^2) with small n would have passed, but obviously cleaner is better.
The live coding round (later in the loop, during onsite) was a 45-minute session over a shared editor with an interviewer on video. They let me use whatever language I wanted. I used Python. The problem was on the harder end of medium, maybe easy-hard. It involved some kind of interval merging variation. Finished with about 8 minutes left and we talked through optimizations.
What I noticed: They want you to communicate while you code. I made the mistake early of going quiet for a few minutes and the interviewer prompted me to narrate. After that I kept talking and it felt much better. Edge cases matter. I got asked explicitly to walk through at least two edge cases before they called time. No trick questions or obscure data structures. This felt like straightforward problem-solving, not trivia.
Comp context: I was applying for a senior role in the Bay Area. The OA was unproctored as far as I could tell.
Overall: not as intense as FAANG coding rounds in my experience. Felt fair.