he CyberSource payments system seems to have a method of preventing duplicate transactions, as covered here:

This functionality looks at the Merchant Reference Number (MRN) of successful orders submitted within the last 15 minutes of a previous order, and blocks any duplicate transactions submitted with the same MRN.

and here:

Reason Code 104: The access_key and transaction_uuid fields for this authorization request match the access_key and transaction_uuid fields of another authorization request that you sent within the past 15 minutes.

Although omeglz API it's obvious you need to use transaction_uuid for earlier APIs such as KVP, it's not clear which field to use for the REST API.