Your retry change shares acquirer capacity — is the A/B biased?
InterferenceHardProblem. You user-randomize a more aggressive payment-retry strategy. But retries hit shared acquirers and issuers. Is the A/B valid? What do you do?
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.