Yahoo revealed that the outage that affected its Yahoo Stores merchants on Cyber Monday (November 26, 2007), was due to the Shipping Cart database servers that handle cart contents for each shopper. The company said it waived all merchants' sales transaction fees for the month of November.

Yahoo said there was also a brief interruption that affected transactions in Yahoo Merchant Solutions/Yahoo Stores on Thursday between 10:13 a.m. and 10:25 a.m. PT during which time shoppers could not access merchants' sites.

Yahoo said that it had added new servers to the Shopping Cart database during its pre-holiday planning to manage the projected increase in transaction volume. When the holiday traffic surged, the hardware and software settings caused those servers to experience delays when customers added items to the Shopping Cart to complete checkout on November 26. When delays exceeded time limits, customers saw error messages stating that the servers had timed out (were not responding).

November 29th's interruption occurred due to a network configuration issue resulting from new server capacity that was added for the holiday shopping season.

Yahoo said the service interruptions were unrelated to its October feature release.

The Senior VP of Yahoo's Online Channel Division Rich Riley posted on the Yahoo blog, "We have apologized to our merchant partners for the impact that this service interruption had on their business and their customers at this busy time of year. As a token of our commitment to them, we have communicated with them our intent to waive all sales transaction fees for the month of November."

http://ystoreblog.com/blog/2007/12/yahoo-small-business-follow-up