The company I work for provides a hosted e-commerce shopping cart solution, SEO-Cart, which supports the USPS Web Tools. Of course the first call coming in for the day was from a client using USPS and having incorrect shipping prices being calculated for their store.
I went ahead and called USPS and the lady who answered was quite rude and explained to me that they had a Worldwide outage which affected other applications than just their Webtools API, and also that they hire a 3rd party company to handle their Webtools API software. She couldn't provide any other information at all and I told her a company of that size should have some sort of fail over plan in place to prevent them from being down as long as they have been. I was really disappointed in the fact she didn't even ask me for my name, phone number, or company by time the conversation was over, but she was probably being bombarded with phone calls all day.
After figuring out that USPS was completely down, I looked through our fail over code and found the following equations seem to come close to the USPS pricing:
National shipping: [cart-weight]*1.6+3.00
International shipping: [cart-weight]*1.6+15.00
These also include pricing for insurance.
After tweaking the fail over pricing code to this, it seemed that everyone using USPS were happy with the results. We also had to decrease the connection timeout set for the request to the USPS Webtools API which was also slowing things down.
The Webtools API seems to be both up and down today, with some orders having shipping prices directly from USPS and others having the fallback pricing. Either way, hopefully their IT department learns from this and also provide us information as to what exactly went wrong.
On that note, this is a prime example that I use when speaking to prospects about the advantages of using a hosted shopping cart solution rather than a licensed/free download solution. Besides the obvious IT benefits that you get with a good hosted shopping cart solution, hosted shopping cart software is typically a centralized application that can provide quick updates to problems like these. Of course this is assuming that the prospect is serious about their online store and doesn't want to handle technical support themselves.