Experiment: The costs of slow build times
Please, step me through this. In a start-up:  a) Developer builds locally
  b) Developer tests locally
  c) Developer pushes to a repository
  d) CI starts
  e) CI ends
  f) Wait for human code review and approval
  g) Merge and deploy
  h) Observe that nothing broke / no need to revert.

Is it even possible for (e) - (d) to be short enough, let alone (f) - (d), to keep the developer's attention instead of context switching? Most devs I know just context switch immediately after (c). If you care about developer productivity, you're much more likely to get results from focusing on (a) and (b), by hooking development laptops into caching and restricting system/test scope, than you are by reducing CI times, unless your CI takes some ungodly amount of time to run (several hours).For point of comparison: article examines how using monster machines can reduce the build time of Fedora to 27 minutes (not really a comparable example to most companies, but OK). My devs complain about an (admittedly unoptimized) CI time of 20 minutes (on a much simpler project than Fedora) that introduces context switching. Is the article really trying to get me to believe that Fedora developers wouldn't context switch on a 27 minute build, twiddling their thumbs for 27 minutes, but that a 35 or 55 minute build would? Something about getting under the 30 minute bar gets developers to keep their focus? I call bullshit.