Question

How would you calculate the actual improvement in network performance after implementing a web cache?

Answer 1

Time to First Byte (or HTML Load Time): Between the time a user attempts to load a page on your site to the time the page is fully loaded, dozens, sometimes hundreds, of different operations will take place. Content needs to be accessed from the server, images need to be retrieved, and style sheets need to be loaded. Before any of these operations can even start, your server must send an HTML document to your users browser to provide the instructions on what actions it needs to take and what files need to be retrieved. The time it takes to deliver the HTML document from your server to your user’s browser is the Time to First Byte (TTFB). An ideal TTFB is around 200 milliseconds which can be achieved when your HTML document is served from a cache.

Time to Title: The title is the name of a page which appears in the browser above the web page address. While this metric is sometimes overlooked as it is only one of many pieces of content that are loaded and displayed to the user, it can go a long way to creating a positive perception in the eyes of your users. Most users have experienced sites that fail to load, have been shuttered, or attempted to access a site with the wrong address. The moment a title is displayed for the page within the browser, anxiety for the user that they may be in the wrong spot is reduced. The longer it takes before the title is displayed, the less patience a user is likely to have while waiting for the rest of the page to load.

Start Render Time: The start render time is an important measure because it indicates when the viewer first sees the page appear in their browser. While the web page may still need to make dozens of additional server request to gather all the content needed, the faster a website begins to render the more likely the user will hang out long enough to load the entire page.

Page load time: The page load time is probably the most common metric used to assess web speed, as it is the easiest to understand. This metric references the time in seconds it takes from the moment a user attempts to access your website until all of the content has been loaded in your browser. The importance of page load time, however, can be overstated, as a user might perceive the page to be completely loaded well before page load is complete. If you have have large images below the fold, or javascript elements loading in the background, your total page load time might be inflated but your user’s experience isn’t impacted. Ideal page load time is under 2 seconds to prevent users from bouncing and increasing engagement across your site.