The scheduling part was fine, global counter for payment IDs is straightforward.
Start by clarifying requirements and constraints, then design the data model and API contracts before diving into implementation details. Focus on correctness, idempotency, and failure handling, and discuss trade-offs between different scheduling mechanisms.
Pro tip: Demonstrate awareness of real-world banking constraints like idempotency, audit trails, and time zone handling; these details show maturity beyond just coding the happy path.
Ask about scale, latency, persistence, idempotency, and failure scenarios to bound the problem and align with the interviewer.
Define the payment entity with fields like id, amount, source, destination, scheduled_time, status, and specify function signatures with return values.
Discuss options like priority queues, timers, or database polling, and justify your choice based on requirements and trade-offs.
Write pseudocode for schedulePayment and cancelPayment, handling edge cases like invalid delay, already cancelled, or already executed payments.
Cover idempotency, concurrency, persistence, retries, and monitoring to ensure the system is robust and production-ready.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.