Back End time is the time required to respond to and generate HTML for the user. This is generally the time spent in the web servers (and therefore also Application and Database servers) as compared with Front End Time which is the time spent at the browser receiving, interpreting and rendering all the assets and content it receives.
Normal Back End to Front End Ratio for most websites is around 20% Back End and 80% Front End. This will increase toward the Back End as the site Front End optimisation improves.
A count of 5XX errors returned by the web servers to Squixa's infrastructure.
Per Wikipedia, "Response status codes beginning with the digit "5" indicate cases in which the server is aware that it has encountered an error or is otherwise incapable of performing the request."
A higher response rate of 5XX errors indicates problems at the origin infrastructure or application.
Offload to CDN considers the hit rate at Squixa's Multi CDN for static objects. The Hit Rate represents the % of static object traffic offloaded to the Multi CDN.
This does not tell the full offload story Squixa delivers for your website as the acceleration tier Squixa runs between the Multi CDN and your origin server provides an additional layer of caching and offload and acts as a shared cache for the Multi CDN. This provides an even greater rate of offload.