FazerCards Glossary
Idempotency key
A client-generated unique value (header `Idempotency-Key`) that tells the server to treat repeat POSTs as the same request — prevents duplicate orders on network retries.
An idempotency key is a unique string the client attaches to a write request. If the same key arrives twice (because the first response was lost), the server returns the result of the original operation instead of creating a second order. Mandatory for POST /order in any production reseller integration; UUIDv4 is the typical choice. Server-side, FazerCards stores key→result for a window (24h+) so retries within that window are safe.
Key facts
- Use a fresh UUID per logical order, not per retry.
- Re-using the same key with a different body is an error.
- Combined with webhook deduplication, prevents double-charging the player.