Chapter 7: Designing Idempotency APIs for Payment Systems
← Previous | Series hub | Next → Chapter 7: Fortifying Payment Systems with Idempotent APIs In E-commerce or Fintech, the ultimate nightmare is not a system crash, but charging a customer twice for a single order. This is usually caused by network lag, an impatient user double-clicking “Pay”, or automated app retry logic. The mandatory solution for any transactional API (Payment/Order) is Idempotency. 1. What is Idempotency? Answer-first: An operation is idempotent if executing it once or N times yields the exact same system state and outcome. While GET and PUT are natively idempotent, POST requires explicit engineering. ...