Quote Originally Posted by njcyx View Post
Maybe my last post is not correct. I double checked the results from my browser's network console, when I selected a different shipping method, File called is "act=ajaxOnePageCheckout & method=updateShipping" Initiator is jquery-3.5.1.min.js. So it looks like JS script is pulled and updated something on the background. My site uses usps and fedex modules. When I select different FedEx shipping methods, the processing time is over 1000ms. When I select different USPS shipping methods, the time is about 800-900ms. When I selected store pickup, the time is only ~100ms. So there is a processing difference between two shipping modules. See screenshot attached.
Click image for larger version.  Name: Capture.jpg  Views: 337  Size: 39.7 KB  ID: 19985
Both the USPS and FedEx shipping methods 'pull' their quotes from the shipping 'supplier'. Depending on how busy the usps and/or fedex sites are, that's where the delay is coming from.