Online retailers stand to make a lot of money on Cyber Monday as long as their infrastructure can keep up with customers. If your company's site goes offline or substantially slows down, you're going to lose sales. And even top ecommerce sites experience performance or stability issues at peak loads, like Cyber Monday, according to Apica's Cyber Monday Web Performance Index.

The Cyber Monday Web Performance Index is built to gauge how well top sites in the market are performing. The purpose is to measure and rank the top-performing retail websites by examining elements like Document Object Model completion time, render time, minimum load time, and maximum load time. This year's index included the Internet Retailer Hot 100, which features a range of the most popular eCommerce sites on the Internet. Cyber Monday is, of course, an ideal day to test as these sites are pushed harder than at any other time of year, creating the right load testing conditions.

Key findings of the Cyber Monday Web Performance Index include:

1. Top 10 eCommerce Websites Are Healthy, But the Rest Are Lagging Behind

The top 10 rated websites are in excellent shape and only show cracks when the servers get overloaded with traffic. However, the servers are able to stay online and continue to function quickly enough to keep visitors on the site. Upwards of two-thirds of visitors will switch to a competitor's site if your company's site is too slow, so this factor is crucially important.

One study found top-rated sites like the Apple Store and Microsoft Store manage minimum load times (two seconds or less) under low-load conditions, but both experienced 10-second load times when visitors pushed the infrastructure under peak demand. Visitors may stick through modest increases, but they are likely to leave when load times explode to Keurig's 38-second, QVC's 131-second, and Avon's 147-second maximum load times.

2. Scaling and Stability Are a Major Issue Across the Industry

Hosting infrastructure that isn't built to scale can produce a very poor "stability" score, meaning there is a very substantial difference in the minimum and maximum load times. Even sites with optimized designs can crumble under demand if the infrastructure can't scale properly.

While the Apple Store's overall performance was fantastic, the site suffered a bit in stability metrics: 1.7-second load times fell to 10 seconds during the busiest periods. Costco's site scaled better, with consistent performance ranging between 1.8-2.9 seconds. Site operators can minimize load time increases with proper load testing and performance monitoring practices. The testing data helps businesses plan scaling infrastructure to grow with demand spikes, while avoiding cases where businesses overspend on more power than needed. 

3. Deception Through Progressive Page Loading Is the Key to Speed

Developers can work with the system by loading the page's basic functionalities as quickly as possible, and its auxiliary components afterward. This way, even if the page takes eight seconds to load, the visitor thinks it only took two.

Costco manages this well. The site's pages are very image-heavy, making it impossible to optimally compress the images and send them to a visitor's system in under three seconds. Instead, the page completes the DOM in just 2.1 seconds, allowing the user to start interacting with the page while the system loads off-screen content faster than the visitor can access it.

Read: 3 Ways to Improve Your Website for Cyber Monday