Merchant settlement and payout batching
Design the merchant settlement/payout system for a payments platform serving 500K merchants. Each day it must net each merchant's captured payments minus refunds, fees, chargebacks, and reserves, then initiate ACH/SEPA payouts on the merchant's schedule (daily, weekly, on-demand). Payouts go out in bank cutoff windows. Describe how a payout amount is computed correctly and immutably, how you guarantee a settlement batch is sent to the bank exactly once, and how you handle a payout that the bank later returns/fails.
What a strong answer looks like
Clarify scale and constraints first. Propose a clean component breakdown, then go deep on the hard parts (data model, bottlenecks, consistency, failure modes) and name the trade-offs you are making.
Clarify5:30 left
Estimate5:30 planned
Design16:30 planned
Deep dive13:30 planned
Failure9:00 planned
Which questions mattered is sealed until you submit. Telling you now would just be handing over the edge cases.
Run or narrate your approach, then ask the coach.