Render time of a webpage can be broken down into two key areas;
- Back End Time - the time it takes for an origin webserver to receive a request and process that request to produce the page HTML.
- Front End Time - the time it takes for the requesting browser to parse the HTML sent and then download, understand and render all the objects which make up the page.
A rule of thumb for Back End Vs Front End is that it usually equals 20% Back End and 80% front end. However, this metric will vary subject to the nature of the website and the level of Front End optimisation.
We compare the performance of front end versus Back End against traffic to understand how increased load may be affecting a back end's ability to serve pages.
We also consider the performance of various page classes to understand how the Back End performance of the system may be affected should traffic skew towards one page or another. Usually, the more transactional pages (such as search or checkout) are higher consumers of Back End computation and therefore slower (from the Back End perspective).