CDN

A CDN (Content Delivery Network) is a geographically distributed network of servers that cache and deliver website content from locations closest to end users, reducing latency and improving page load speeds. It stores copies of static assets like images, CSS, JavaScript, and videos across multiple data centers worldwide.

Meaning & Context

CDNs work by routing user requests to the nearest edge server rather than the origin server, significantly reducing the physical distance data must travel. When a user requests a webpage, the CDN serves cached content from a nearby location while only retrieving uncached or dynamic content from the origin server. Modern CDNs also provide additional services like DDoS protection, SSL/TLS encryption, and real-time analytics.

Why It Matters

For A/B testing and CRO, CDNs are essential for maintaining fast page load speeds, which directly correlate with conversion rates and user engagement. Many enterprise A/B testing platforms operate at the CDN edge layer, enabling faster variation delivery and reduced flickering. However, CDN caching can complicate testing by serving stale content or causing inconsistent experiences if cache invalidation isn't properly managed.

Example

An international e-commerce site uses a CDN to serve A/B test variations globally. Customers in Australia load the page in 1.2 seconds from a Sydney edge server, while European customers load from Amsterdam in 0.9 seconds, compared to 4-5 seconds if everyone accessed the origin server in Virginia. This speed improvement increases conversions by 8% across all markets.