As the kings of high performance, Google has given us many tools and enhancements that have benefited the web world enormously. Google Chrome (as of 2017) has over 60 percent of the browser market share and its drive for performance has forced other browsers to play catch-up.
Not to be outdone at the server level, Google also has vested interest in ensuring that websites are highly performant as well. This is because faster sites offer a better user experience, which is important when you're trying to offer highly relevant search results. To expedite this, Google released ngx_pagespeed, which is a module for NGINX that tries to apply Google's best practices to reduce both latency and bandwidth for websites.
While many (if not all) of these optimizations can be manually applied, or should be part of any highly-performant development workflow...