I enjoyed listening to Jim Keller.  About the interviewer Lex Fridman i would say, you have to learn to look at your subject when you're talking to him.  Lex is often looking down. I don't know if he is intimidated by the person he's talking to, that's the appearance it gives,  or if he has trouble thinking and looking at his subject at the same time. It's not a good habit.  I enjoyed this video and I'll be back.