Meta
Product sense plus very large fan-out. Expect social-graph shaped problems, expect the celebrity-user case to come up early, and expect to be pushed on what the user experiences rather than what the diagram says.
How they weight it
Requirements and Design, with fan-out and hot keys as the recurring pressure point.
Closest interviewer archetype: The Pressure Tester — Questions every decision. Keeps asking "why not the other way?"