Preparing for the Holidays: A 101 in Web Performance Optimization

Holiday sales traditionally constitute a huge portion of retailers’ annual revenue, and there’s a lot at stake in the upcoming season. According to PwC, web sales for the overall retail sector will see a mid- to high-teens percentage increase over last year, with the leading retailers poised for a 40 percent to 50 percent increase.

Not surprisingly, retailers are focusing heavily on optimizing the performance (speed) and availability of their websites and mobile sites. A retailer’s web presence is like its digitial “front door.” When a consumer has a bad experience — encountering a site that's slow, cumbersome or not conducive to conducting transactions in any way — they're likely to abandon the site and look elsewhere for their shopping needs, often permanently. IT and operations teams face tremendous pressure to ensure that websites and mobile apps exhibit superior performance during the holidays. However, pulling this off is far easier said than done. Fortunately, there are several straightforward steps that retailers can take to put themselves in the best position for success.

Load Testing Data Center Infrastructure and Native Site Content is Critical … But Not Enough
Load testing web serving infrastructure and all of the native functionality on a website is key to ensuring preparedness for peak traffic. Most retailers know this and conduct load testing across key conversion paths, as well as any new, previously untested features whenever a traffic spike is expected. Yet every holiday season it seems there are stories of major retailers’ sites going down. This is because even if infrastructure and in-house functionality is thoroughly load tested and proven to be sound, websites are still highly vulnerable to failures.

Much of this has to do with the growing complexity of online systems. An increasing number of sites are outsourcing a large portion of their services such as DNS, CDNs and third-party services like tracking pixels and social media widgets. Yet every third-party vendor represents an additional connection that must be made for the page to fully render, and therefore added potential for something to go wrong. More specifically, even if all of a retailer’s in-house servers can handle a holiday-driven traffic spike, the site can still be impacted by the failure of a lesser-equipped external third party. Remember, a heavy traffic period for one retailer is likely a heavy period for other retailers. This means the third-party services supporting them like CDNs are often under the heaviest pressure of all.

Load tests — and all website testing for that matter — must be able to demonstrate how the performance of individual third parties impacts the overall performance of the page. This is the key to vetting third-party services during both peak and nonpeak periods, as well as setting and enforcing service-level agreements once a third-party service is activated.

Keep Third-Party Services in Check
While advanced features and functionalities can create a richer end-user experience, as noted previously, each one also presents liabilities that should be avoided (unless absolutely essential) during critical revenue-generation periods. For these reasons, third-party tags should be kept to a minimum.

For those third-party services that are deemed necessary (e.g., IaaS providers like CDNs and DNS), backup systems must be in place and ready to be enabled in the event that your primary provider experiences performance issues of its own. And for the third-party tags that live on the pages themselves and are deemed necessary, careful page construction offers a way to minimize the impact of a potential performance slowdown or failure. Third-party tags should be placed at the bottom of the page after the onload event fires so that if they do fail, they won’t affect users ability to interact with the site. If a third-party performance degradation is particularly worrisome, retailers must also have contingency plans in place that allow them to quickly isolate and remove the element from the page.

Slimmer is Better
The weight of web pages (aka the total amount of bytes that are being delivered) is another huge factor in determining site speed. The more bytes that are being delivered, the more time it’s going to take for the page to fully render. That’s why whenever a high-traffic period is approaching, IT teams should be focusing on slimming down through image optimization, elimination of any extraneous elements, and compression of all text-based content like HTML, XML, JavaScript and CSS. Other optimization techniques include enabling HTTP Keep Alive for persistent TCP connections, reducing the number of roundtrips that the browser must make, and domain sharding (but no more than two domains). Domain sharding entails splitting resources across multiple domains, which helps improve page load time .

Keeping slim is especially critical for mobile sites. Mobile networks tend to be much more strained than landline internet providers, so the impact of bandwidth-hogging website elements can be even more detrimental for the end-user experience. Site content must therefore be kept ultralightweight for mobile users. This can be accomplished by creating a separate m. domain to which all mobile traffic is directed — it’s a way slimmed-down version of a desktop website — or opting for adaptive design, wherein there’s one website that detects device types and then filters and delivers content based on the constraints and limitations of individual devices.

The internet has grown increasingly complex and interdependent in recent years. In many ways this enables richer, more satisfying, improved user experiences. But it also comes with an undesirable side effect: a small outage or degradation anywhere in the chain can spell disaster for end users anywhere in the world. This is especially true during the holidays, when the broader infrastructure of the World Wide Web creaks under load.

History has shown that even the most well-engineered websites can fall victim to elements outside of their control, especially during the holidays. It's impossible for retailers to protect themselves from everything; therefore, they must focus on protecting themselves as much as is humanly feasible. The “Performance Optimization 101” techniques described above are a positive step in that direction

Mehdi Daoudi is the CEO of Catchpoint Systems, a web performance monitoring solution provider.