Copied from https://phabricator.wikimedia.org/T97570#1265298
"The size of the HTML served at pageload seems to be where the biggest performance gains are to be had on mobile web at the moment. One area to explore is the automated size reduction of the HTML via Parsoid. Another is to only serve the lead section on pageload and load the rest of the page asynchronously. A secondary improvement-worthy area is the current firstPaint performance hampered by the amount of CSS and JS served in the head. Some of which has already been identified as low-hanging fruit. Lastly, the idea of loading images on demand when they are scrolled to could be experimented with."