Design an end-to-end loan application system for a small online lending platform. Users choose among different loan products and submit applications; the system performs internal review/underwriting and integrates with third‑party providers to fetch credit history and bank‑account transaction data. Describe: ( 1) the high‑level architecture (service boundaries, data models, APIs, queues/workflows/state machine); ( 2) the approval/denial path and post‑decision actions, including funds disbursement/transfer; and ( 3) operational concerns: idempotency, retries, timeouts, rate limiting, and handling partial failures when calling external APIs. Explain how you will implement KYC/AML and fraud checks, protect PII and meet compliance/audit needs, support manual review tooling, and ensure observability, scalability, and backpressure under growth. Compare synchronous vs asynchronous processing and justify trade‑offs.