In plain language
It makes retries safer by ensuring a timeout or duplicate event does not create the business result twice.
Example
Two delivery attempts with the same order key create one invoice rather than two invoices.
Related terms
Deduplication · Webhook · API
Common misconception
Idempotency does not mean a request runs only once; it means repeated processing does not multiply the intended effect.
Implementation guidance
Generate a stable key at the business-event boundary, store processed keys, use provider idempotency headers, and define a retention window.