Securing Payment APIs: How Idempotency Keys Eliminate Duplicate Charges and Lost Orders

Network timeouts and retries can cause duplicate charges and lost orders—two outcomes that erode user trust and business credibility. Idempotency keys offer a simple but essential pattern: by attaching a unique identifier to each request, servers can safely deduplicate retries without re-executing operations. This is crucial for any API handling payments, bookings, or state-changing transactions where failure is not an option.