Server response time, also called Time to First Byte (TTFB), measures the length of time it takes the server to send the first byte of data to the browser. If this process takes more than 600ms, Lighthouse will trigger the warning. If the server must do a lot of work prior to sending data, like querying databases, processing, code, building the page, etc., it will just add more time to the page load process and frustration to the user. And this does not take into consideration what kind of connection the user has. Seeing a blank page for several seconds is never a good impression for users.
Reduce Initial Server Response Time
What is Server Response Time?
How to Reduce Initial Server Response Time
There are a few factors that can contribute to slow server response times, such as network speed, application code, and the server itself. Each of these factors should be reviewed to identify where the bottleneck is occurring. It could be inefficient code or simply that a hardware upgrade is necessary. One way to reduce initial server response time is to make use of caching rather than making the server generate a new page each time it is requested. Some server frameworks, like Drupal, Magento, or React all have specific ways to enable this. Also, CMS platforms like WordPress contain a variety of plugins and themes. While these are great for creating development efficiencies, they could be contributing to server response time, so review which plugins and themes you are using.
It is important to note here that these optimizations may require in-depth knowledge or support from third-party resources. You do not want to create unintentional errors here and inexperienced web developers could do more harm than good.
Lighthouse is an open-source tool that is used to run an audit against your web pages and provides scores and suggestions for improving page performance, accessibility, SEO, and more.
PageSpeed Insights is a tool created by Google that reports on the performance of a page on both mobile and desktop devices, and provides suggestions on how that page may be improved.