Why it matters for your business
Retries and duplicate events are normal in automation. Webhooks get redelivered, network calls time out after the receiving system already acted, and workflows get rerun after an error. Without idempotency, each of those can create a second invoice, a double payment or a repeated customer email. Asking whether a workflow is idempotent is one of the most useful technical questions a buyer can ask, because it separates automations that recover cleanly from ones that need someone to clean up duplicates by hand.
Example
An automation creates a bill in the accounting system for each approved vendor invoice. During an outage, the accounting API accepts a request but times out before replying, so the workflow retries. Because the workflow first searches for an existing bill with the same vendor and invoice number, the retry finds the bill already created and skips it instead of recording the invoice twice.