Performance Edge makes experiments run faster by moving experiment processing from the browser to the edge (CDN). In our testing, we’ve seen web experiments using Performance Edge load in less than 50 milliseconds (faster than the blink of an eye).

Performance is core to user experience

Website speed matters. Fast loading sites are essential to a great user experience. Studies show that faster loading websites correlate with better conversion rates and less abandonment.

However, customer experience is not just about speed, it’s also about how intuitive your site is for your visitors and how effective it is at helping them find what they need. Companies like StubHub and Realtor.com use experimentation to validate and drive improvements in customer experience. We surveyed over 800 decision-makes at companies over 500 employees and discovered that companies that run over 20 experiments/month see over a 14% revenue increase compared to companies that run less than 20 and only see 1-4% increase in revenue.

One challenge with running a lot of experiments is that it can begin to impact site performance. Because we know how critical performance and experimentation are to helping you improve your customer experience, We’ve been on a mission to make Optimizely run faster on your site. We’ve made a number of improvements and provided more options for maximizing your performance. 

How web experiment performance works

When you create experiments in Optimizely Web, the experiment instructions are stored in a JavaScript file called a snippet. When a user visits your site, their browser downloads the snippet from Optimizely’s CDN and evaluates it to determine what experience to deliver. As the number of experiments grow, the snippet also grows in size because it includes information about all experiments. The larger snippet results in more time to render the experiment which can impact site performance. 

Scaling performance with an experiment delivery network

To deliver a smaller, faster loading snippet, we built an experiment delivery network (EDN). The EDN makes experiments render faster by moving experiment evaluation from the browser to a worker on the EDN (see Fig 1 below). Using this technology, we are able to deliver a microsnippet with only the variations needed for that visitor. As a result, the experiments render between 2-20x faster. Most importantly, as teams scale experimentation, performance scales as well.


Figure 1: The experiment delivery network shown on the right, returns a microsnippet with only the variation data for that visitor, reducing the time to render the experiment and results in faster site performance

The experiment delivery network is powered by Cloudflare Workers. Cloudflare Workers run code at the edge of Cloudflare’s global network, which spans 194 cities in more than 90 countries, with extremely low latency. The EDN ensures that no matter where your customers are, you are able to deliver experiments quickly.


Figure 2: Powering Optimizely’s experiment delivery network with Cloudflare’s Global Network

Interested in learning more?

Existing Optimizely customers can reach out to your account team. Companies not yet using Optimizely can connect with us to learn more about how Performance Edge can help them increase experiment velocity while ensuring optimal site performance. 

You can also find more information in our developer docs.