Completed a Box onsite loop a few months ago for a senior SWE role. The whole thing is virtual now, has been for a while. Wanted to give a realistic picture because I went in with incomplete info.
Structure (senior IC, your mileage may vary by level and team): 45 min live coding, one interviewer 60 min system design, two interviewers 45 min behavioral, one interviewer 30 min hiring manager conversation
All done over two half-days. They split it across days and I actually appreciated that. The second day felt less exhausting than when I've done 5 straight rounds at other companies.
Some notes on each:
Live coding: Python or whatever you're comfortable with. Medium difficulty graph problem. They let me look up syntax (not solutions), though I didn't need to. Feedback I'd give myself: get to a working solution first before optimizing. I spent too long on O(n) when O(n log n) would have been fine, and it made the time feel tighter.
System design: Box-flavored. Think enterprise file collaboration. They probed hard on permissions and consistency. Two interviewers and one did the bulk of the questioning. The other asked about operational concerns near the end: how would you monitor this, what would cause an incident. Good question, caught me slightly off guard.
Behavioral: felt like a genuine conversation. The interviewer was good. They pushed on specifics but it didn't feel like a gotcha session. One question was essentially "tell me about a time you had to convince leadership to change course" and they followed up like four times on the outcome and what I'd do differently.
Hiring manager: mostly a conversation. What kind of work I was hoping to do, where I saw myself in a few years, questions I had about the team. Felt more like a mutual fit check.
Took about 10 days to hear back after the final round. That's the part that will test your patience.