Lots of coding on the whiteboard, very detailed and specific questions about Linux administration and low-level, core system functionality such as I/O buffering. There were also questions about security and safety of servers, including handling of logs. Be mindful of how you speak and avoid expressing strong opinions on what might or might not be a good idea -- Googlers work in an entirely different universe and may interpret you wrongly. I got a guy angry at me because I said external logging in a very high load webserver would be a very bad idea, given the additional I/O time. It was 2010 and I always had to make do with smallish servers and 100mbps ethernet; when you have a slashdotted website crawling to death you might even stop logging to the disk to keep your server online. Said Googler surely worked with huge datacenters and gigabit connections, and thought I was stupid. But all in all, the experience was nice.