Why CDN visitor prioritization doesn't cut it in ecommerce

CDNs are a great web perf tool. But ironically, the strength of using a CDN for improving web performance is its weakness for serving as a virtual waiting room. Find out which 2 major shortcomings of CDN visitor prioritization should make you wary of using it with your customers.

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There’s no doubt content delivery networks (CDNs) are a critical tool in your ecommerce toolkit. We’ve even listed using a CDN as the first of 11 essential steps to building performance into your website. CDNs improve website performance, reliability, and security and allow your website to handle more website traffic. Solid website performance is key when running high-traffic sales, product launches, and collection releases.

Many CDNs have expanded beyond caching for web performance and have become reverse proxies. CDN reverse proxies can now also run code that broadens their functionality, including load balancing and DDoS protection.

Since it’s likely you already have a CDN reverse proxy, you could be tempted to make the mistake of leveraging a CDN reverse proxy to throttle high traffic. Something like Akamai’s visitor prioritization cloudlet sends shoppers to a waiting page during periods of high traffic. But the very way a CDN reverse proxy is designed to improve web performance makes it poor for running a virtual waiting room. You’d be at risk of giving your customers a poor user experience.

Here’s why your CDN’s virtual waiting room doesn’t cut it in online retail and one way to better deal with online traffic peaks instead.  

CDN visitor prioritization doesn't provide a first-in, first-out (FIFO) wait (and won't anytime soon)


Ironically, the strength of using a CDN reverse proxy for improving web performance is its weakness for running a virtual waiting room.

When a customer visits your site, static pieces of the page like images and videos load from the CDN’s servers instead of the servers hosting your website. This frees up your own servers to do the heavy lifting required to process online purchases.

A CDN reduces the time for your content to load on your customer's browsers by geographically spreading your website content on servers across the globe. Customers’ browsers communicate with your website at servers close to them, what’s called the network edge. The key takeaway here is that CDN reverse proxy network is decentralized.

Map example of cdn edge servers connecting to origin server

To create a fair first-in, first-out (FIFO) wait, the virtual waiting room needs a centralized overview of all traffic requests to your website. That way it can track the order of all traffic, assigning an accurate place in line to your customers and determining who should be the first ones out of the online queue.

What does this mean?

When a CDN reverse proxy places shoppers in a waiting room during periods of high traffic, your shoppers are not placed in a logical order or sequence. Importantly, this also means there’s no way to give an informed estimate of waiting time to your shoppers.

Instead, the CDN reverse proxy tries to compensate by rate limiting. It uses complex rules to take a random set ratio of visitors at each edge location through to your website.

But traffic isn’t equally spread around the world. In practice, this means that how quickly visitors get through to your website depends on traffic levels in their area. For example, if traffic to your site is heavy in Phoenix but light in Philadelphia, the Philadelphia visitor could get put through to your website even while visitors in Phoenix who arrived earlier are held to wait on a waiting page. 

First-in first-out virtual waiting room vs. CDN reverse proxy visitor prioritization

Why is this a problem?

CDN-based virtual waiting rooms fall short on providing fair and informed waits. Unequitable and uncertain waits feel longer than fair and certain waits. Fair and certain waits drive a higher level of customer satisfaction, retention, and, therefore, conversion.

A CDN reverse proxy virtual waiting room doesn't capture customers at the page-level

When you have a popular online event, it would be ideal to place the virtual waiting room at any point where website bottlenecks occur. For retailers the worst of these are typically the payment gateway and transactional database.

CDN reverse proxy virtual waiting rooms only address the total number of requests to the whole website.

What does this mean?

All customers browsing on your site end up captured by the waiting room. There can be merits to queuing all traffic on your entire site, for example on Black Friday. But a CDN reverse proxy virtual waiting room like Akamai’s visitor prioritization doesn’t provide you with an alternative option for other, more specifically mapped high-traffic events. This could be a limited-release sale located on a separate page of your website, for instance.

Why is this a problem?

In this case, you already know that the products offered in the limited release sale will sell out. Your goal is to also drive sales on your high-margin products. It’s important then to avoid placing other customers who are only interested in your other high-margin products into the waiting room.

How to manage online traffic better

If you’re an online retailer dealing with online traffic surges, first: congratulations! High traffic means you’re connecting with your customers. But it’s also a challenge you need to respond to if you’re going to keep those customers.

There are ways to build performance into your website, and there are steps you can take in advance of big sales events to ensure your business is ready.

CDN visitor prioritization is not a smart way to deal with traffic peaks. But there are several virtual waiting room solutions on the market that let you manage traffic in a tailored way while giving your shoppers a fair customer experience.

(This post has been updated since it was originally written in 2016)

See how Queue-it compares with CDN visitor prioritization