Here's the problem with whiteboard interviewing. You can't see how I think. It's just not possible. I'm trapped in a box with a strange person who is staring at me & asking me really invasive questions. If you wanna know whether or not I know about optimistic locking, just ask me "do to know about optimistic locking well?". If I do, ask me an optimistic locking question of modest difficulty. If I don't, don't spend an hour trying to get me to move in that direction and see if I figure it out. I'm just gonna think you're trying to show off how smart and unprepared you were.