Measuring CDN Performance With Real Users
This is cross posted on the Wayfair Engineering Blog A couple of weeks ago I ran a test with WebPagetest that was designed to quantify how much a CDN improves performance for users that are far from your origin. Unfortunately, the test indicated that there was no material performance benefit to having a CDN in place. This conclusion sparked a lively discussion in the comments and on Google+, with the overwhelming suggestion being that Real User Monitoring data was necessary to draw a firm conclusion about the impact of CDNs on performance. To gather this data I turned to the Insight product and its "tagging" feature. Before I get into the nitty-gritty details I'll give you the punch line: the test with real users confirmed the results from the synthetic one, showing no major performance improvement due to the use of a CDN. Implementation Details: Prior to this test we served our static content (CSS, JS, and images) from three domains: common.csnima