Its very hit or miss with this place. I've had great experiences here before but this time, I seem to have been paired with someone who's left a huge negative impression. I've had the pleasure of interviewing with some big names in the industry, eg one of the department heads at Bridgewater Associates as well as one of the big name quants at Bain Capital, people with proper track records behind them, well known in the industry. They were professional and polite the whole way through. The interview at Millennium was a huge eye opener that some jerks have still managed to remain. It was some unnamed mook of a quant, no claim to fame, no visible track record. But he started huffing and getting exasperated 10 minutes into the interview. Like dude, if the big shots can keep it clean for 2 hours, you can at least try and get through 30 minutes with your ego in check. Within the first 5 minutes, I knew I wouldn't want to work in that team... so I guess that's a positive? The question was basically a variation of the trapping rain water leetcode problem. Just remember, don't ask any questions or this guy will get mad you interrupted him