I started with the happy path and got pretty far before they pushed on the compliance angle.
Start by clarifying requirements and scope, then design a high-level architecture that separates concerns: user-facing APIs, transfer orchestration, compliance, FX rates, and payment rails. Dive into the two highlighted challenges—country-specific restrictions and real-time FX—by discussing data models, caching, and integration patterns, and wrap up with trade-offs and scalability considerations.
Pro tip: Emphasize idempotency and exactly-once processing for transfers, as money movement demands strong consistency and failure recovery; also mention how you'd handle partial failures in a distributed transaction.
Ask questions to understand scale, supported countries, currencies, compliance needs, and latency requirements. Define functional and non-functional requirements to guide the design.
Sketch the main components: API gateway, user service, transfer service, compliance service, FX service, payment processor integrations, and ledger. Explain how they interact to initiate and complete a transfer.
Design a rules engine or configuration service that encodes per-country limits, required documents, and prohibited corridors. Discuss how to keep rules up-to-date and enforce them at transfer initiation and completion.
Describe how to fetch rates from providers, cache them with appropriate TTL, and handle failures. Discuss rate locking, spread, and how to ensure consistency between quoted and executed rates.
Discuss trade-offs like consistency vs. availability, latency vs. accuracy, and build vs. buy for FX and compliance. Outline scaling strategies for high throughput and global distribution.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.