This is interesting, but means very little to me as a heavy user of Docker.

I don't care about boot time. I care about 1) build time, and 2) ship time. In Docker, they are both fast for the same reason.

At the top of your Dockerfile you install all the heavy dependencies which take forever to download and build. As you get further down the file, you run the steps which tend to change more often. Typically the last step is installing the code itself, which changes with every release.

Because Docker is smart enough to cache each step as a layer, you don't pay the cost for rebuilding those dependencies each time. And yet, you get a bit-for-bit exact copy of your filesystem each time, as if you had installed everything from scratch. Then you can ship that image out to staging and production after you're done locally--and it only has to ship the layers that changed!

So this article somewhat misses the point. Docker (and its ilk) is still the best tool for fast-moving engineering teams--even if the boot time were much worse than what they measured.