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When you use Amazon FPS, there are times when you should store important information in your database. The following sections describe some important values you should store.
The CallerReference is a string you provide that
uniquely identifies a request. An appropriate value to use is the order ID. You can also use the value to retrieve information about a transaction or to retrieve the related token (for more information, see Co-Branded Service Requests that Don't Return). Amazon FPS uses the caller reference value to provide request idempotency for a seven-day period (for more information, see Resending Requests).
![[Note]](images/note.png) | Note |
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If you perform multiple partial refunds for a particular payment, you must provide a different caller reference value for each partial refund request. |
The transaction ID is a string Amazon FPS creates to uniquely identify each transaction in the FPS system.
The Co-Branded service doesn't return a transaction ID; only Amazon FPS does (e.g., in a Pay response). You should maintain the
transaction ID in your database and associate it with your
caller reference value for the order. Because of network issues, it's possible that the response to your Pay call might not reach you, so you won't have a transaction ID to store in your database. In that case you can resend the original request (within 7 days) and receive the response again (for more information, see Resending Requests).
Amazon FPS returns a request ID for each Amazon FPS API call accepted for processing. If you have a problem with a request, AWS asks for the request ID to troubleshoot the issue.
