Start by clarifying requirements and scale, then outline a high-level architecture with core services like payment processing, ledger, and external integrations. Dive into key components such as idempotency, consistency, and fault tolerance, and discuss trade-offs for scalability and reliability.
Pro tip: Emphasize idempotency and exactly-once processing for financial transactions, and discuss how you'd handle reconciliation with external rails to ensure data integrity.
Ask questions to understand expected transaction volume, latency requirements, consistency needs, and supported payment methods. Define functional and non-functional requirements.
Sketch a service-oriented architecture with components for payment processing, ledger, wallet management, and external integrations. Consider using event-driven patterns for scalability.
Detail the design of critical parts: idempotent APIs, distributed transactions, ledger design for double-entry accounting, and handling of refunds/chargebacks.
Discuss partitioning, replication, caching, and asynchronous processing. Address failure modes, retries, and reconciliation with external rails.
Highlight trade-offs between consistency and availability, latency and durability, and how the system can evolve with changing requirements.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.