Speed optimization is frequently a part of SEO issues. Google has been using site speed signals in its search ranking algorithms since 2010. The biggest search engine in the world believes that faster websites create happier users. Their internal study showed that when a website responds slowly, visitors spend less time there. The correlation between the response time of a website and its position in search results is becoming undeniable. The famous "mobile-friendly" philosophy of Google is also to consider loading speed as a key indicator of its page ranking system.
Going further, several tools were proposed by Google to identify and optimize the speed performance of a website:
Google Analytics and its Real User Monitoring features to monitor the loading speed of your website
PageSpeed Insights, which allow you to diagnose your performance
Google WebMaster Tools, which show the access speed of a Google Bot during its crawl on your website