Why did I receive a 409 HTTP response to my idempotent API request instead of 429?

Previously, the Checkout.com API returned a 429 – Too many requests  HTTP response for duplicate idempotent requests.

For this particular scenario, this has been replaced with the 409 – Conflict with another request being processed HTTP response.

The 429 – Too many requests response now only refers to rate limit issues.

For more information, see the HTTP status codes and API rate limits documentation.