Most credit card processing applications and gateways implement some type of logic to recognize, and optionally block, what are potentially duplicate requests within a short amount of time for the same card and amount. Is there any logic like this implemented in the remote-pay-windows REST service? If so, can you provide direction on how to implement this duplicate checking and any related override for it?
The Clover Mini will flag suspected duplicate payments. As it's implemented now is not optimal though. The message is displayed on the customer-facing device giving them the option of voiding the payment. The proper solution would be to have a handshake between the terminal (Clover Mini) and the POS to let the merchant accept or reject the suspected duplicate. I'll file an internal issue to flag that, but in the mean time the message will be displayed to the user.
Any payment with an hour that has the same first / last 4 on the credit card will be flagged. The logic is not customizable.
The 1.0 SDKs additionally require an "externalPaymentID" to be passed in by the integrator with every transaction. We'll check that the ID passed in isn't identical to the previous ID (we only store 1 ID at a time for these checks). This allows you to customize the duplicate checking logic any way you like, since you're in charge of creating the ID.
