The fourth quarter is crucial to many retailers’ long-term success, which is why any slipup during the holiday season can carry outsized implications.

Take Costco Wholesale Corp., which encountered a number of challenges throughout the week of Thanksgiving. began experiencing intermittent slow load and transaction times late Wednesday evening, according to site monitoring company Catchpoint. Then, many shoppers were unable to get anything on its site to load for a brief time early morning Thanksgiving. The retailer’s issues appeared to end around 7:15 p.m. EST Friday, before intermittent problems arose for a short time Saturday afternoon.

During the issues, a banner on its site read: “The website is currently experiencing longer than normal response times. Please note that all Thanksgiving Day-only promotions have been extended into Friday, November 29th, WHILE SUPPLIES LAST. We apologize for any inconvenience.”

Once its homepage was up and running, Costco continued to experience problems; its search results page, product detail pages and the shopping cart page operated significantly slower than normal. Costco acknowledged its difficulties with a banner on its side that read: “Sorry for the Delay. is having a busy day! Hang on!! You are in queue, and we’ll get you to where you were going in just a minute.”

Altogether, Costco’s downtime—which Catchpoint defines as an inability to complete a transaction—totaled 17 hours.

The performance was “unfortunate,” said Richard Galanti, the retailer’s executive vice president and chief financial officer in a conference call with analysts a few weeks later. “Despite all the efforts to have plenty of processing capacity … there was something that occurred.”

To salvage some of the damage, Costco extended its Cyber 5 deals an extra two days, which Galanti believed helped the retailer generate additional revenue. However, there were significant repercussions for those glitches; while Galanti says Costco’s ecommerce sales rose by a “high teen” percentage, the issues likely drove a number of shoppers to other retailers’ sites to make their purchases, says Bob Buffone, chief technology officer at mobile optimization company Yottaa. On Thanksgiving, for example, Buffone estimates the retailer’s online sales were about 40% less than they typically would have been.

While site performance is always important, it’s especially critical during the holidays when consumers are eager to buy and will likely turn to another retailer to get what they need if they encounter any hiccups. For example, 57% of shoppers have left a slow-loading ecommerce site and then bought from a similar retailer, according to 2019 Retail Systems Research survey of 1,300 U.S. consumers. And 23% said they never returned to a brand’s website due to slow page performance.

“Monitoring one’s website and ensuring it keeps pace with the industry is essential for growth given its impact on where consumers buy,” says Lauren Freedman, senior consumer insights analyst with Digital Commerce 360.

To get immediate access to the rest of this article, sign up for a free Strategy Membership using the Join for Free button below. If you’re already a member, please sign in.

Want to read more? Unlock Free Strategy Membership