Randomize the guest or the listing? The choice changes your answer
Test selectionHardProblem. For a marketplace change, you can randomize on the guest side or the listing side. How do you choose, and how does the choice affect bias and variance?
Before you reveal: say your answer out loud, as if you were in the real interview — get your reasoning across clearly first. There is no single correct answer: reading what the interviewer is really after and defending your own thinking is what makes an answer strong.
Strong-answer signal: recognizing that guest-side and listing-side randomization leave supply- vs demand-side interference, matching the design to the scarce side, and treating it as a joint bias/variance decision. Common trap: defaulting to user-level randomization with no awareness that the side you randomize determines which interference biases you.