When a customer clicks to complete a purchase, if anything happens that prevents the confirmation page from loading (user temporarily loses internet connection, etc.), but the purchase is still completed, and the credit card has been charged, what is the best way to prevent the customer from making a duplicate purchase (assuming that the first attempt failed)?
1) Whenever a customer makes a purchase, check to see if an identical purchase has been processed. If so, notify the customer and ask if they wish to proceed.
2) When a confirmation page fails to load, have something time out on the purchase screen, and ask customers to check their email for a confirmation, to see if the purchase was successful.
3) Some other better option...?