not really, the speed of the checkout process is determined how quickly the web server can create a cURL connection to the gateway server to send the order details over, there may be a number of other stores that are also trying to access the gateway server. the gateway server then has to contact the merchant bank for the site visitors credit card to process the transaction, once the merchant bank sends the result to the gateway, the gateway can send the result back to the Website and direct the user to the success or failure page.
There is a good deal of processing that needs to take place.