Idempotency-Key Header Added to Scalingo API v2 (2024.02) – Retention Period and Endpoint Coverage Questions

Goal: ensure that a transient failure on a mutating POST request to Scalingo’s API does not create duplicate resources when retrying.

Uncertainty: the Idempotency‑Key header was introduced in platform release 2024.02 for v2 endpoints such as /apps and /addons, but the documentation notes that the key is persisted for approximately 24 hours and that this retention may vary by region or future updates, and not all provisioning APIs have been upgraded.

Questions:

• What is the exact, guaranteed retention period for an Idempotency‑Key across all Scalingo regions and platform versions?
• Which POST endpoints in the v2 API currently honor the Idempotency‑Key header, and where is the authoritative list published?
• If a request is retried after the key has expired, does the API return a specific error (e.g., 409 Conflict) or does it treat the request as a new write?