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.