A few weeks ago I noticed that Linear got slower than it used to. Especially on the new Diffs feature, that we were getting ready to release, it was pretty bad. For days I was running profiles, staring at profiles, bisecting with agents from every direction. The pattern was clear - we accessed the DOM a ton, which blocked the main threads on style recalcs and layout for 10s or 100s of milliseconds over and over. I shipped dozens of PRs to get rid of those layout-causing calls, using pretext and whatever tricks the agents and I could come up with. It helped, but only a bit. I was getting desperate.