Idempotency in HTTP APIs: Safe Retries with Idempotency-Key Headers
Prevent duplicate credit card charges and double-orders with Idempotency-Key headers in REST APIs. Architecture design and Redis implementation.
If a user clicks "Submit Order" and their mobile internet drops for two seconds, their app might retry the request. Without idempotency, the user is charged twice. An Idempotency-Key header ensures that duplicate requests within a 24-hour window return the cached initial result rather than charging again.