Design booking and settlement systems

You may be asked one or more backend-heavy system design problems such as: 1. **Design a reserved-seat ticketing platform** similar to a concert or sports booking system. - Users should browse a venue seat map, select seats, place a temporary hold, and complete checkout. - Explain how you would prevent **double booking** when many users try to buy the same seat at once. - Discuss the API design, what the backend should return, and how the frontend should render seat availability and user-facing seat states. - Cover failure handling, hold expiration, and the user experience during contention. 2. **Design a transaction reconciliation system**. - The system periodically receives files from a bank and from a payment processor. - Each file contains transactions that must be compared against internal orders/payments. - Detect missing, duplicate, or mismatched records, and produce outputs for operators or downstream systems. - Discuss file ingestion, matching logic, auditability, and fault tolerance. 3. **Design a remittance-file processing system**. - A remittance file contains many transactions. - For each transaction, validate it, enrich it with additional data, store the result, and notify humans or downstream systems when needed. - Discuss orchestration, retries, idempotency, partial failures, and reliability.