It wasn't the focus of the presentation, but the title brings up one other part she didn't cover explicitly. My kneejerk response at seeing the title was "how could it possibly take 10 years just to learn DNS, if you're actually spending some nontrivial amount of that time trying?"
This might be partly because I have knees, and am a jerk. (But aren't those true of most of us?)
And I'm kind of right. Understanding enough DNS for most practical purposes should take far less than 10 years, even if you really are spending 6 months at a time ignoring it (as jvns says in the talk). And that might be enough, who knows.
But there are so, so many things where when you actually try it out, or need to scrape down a layer because you're using some additional feature, you suddenly find that the stuff you thought you understood is actually perched atop a shifting layer of incandescent hairballs.
For me in the specific case of DNS, one time my smug confidence was shattered was from a previous jvns presentation, where she demonstrated that my naive mental model of DNS cache TTLs was not only wrong, but didn't even make logical sense. (This isn't the negative caching from the talk, it's boring positive cache results where the TTL only starts counting once something gets put in the cache.)
That's a general pattern for so many technical things. The performance of your non-IO code is based on the number of instructions and the instructions per cycle. Oh wait, it isn't, you can pretty much ignore the instructions and just count memory references. Er, no, memory references aren't equal, you need to count up how many hit each level of the memory hierarchy. No that's not it either, some of those slow things don't seem to matter, I guess it's all down to data dependencies. Wait a minute, this code isn't accessing much memory at all, but all these integer divides are bogging things down, maybe I do need to pay attention to the instructions... I could go on. Those hairballs are getting kind of bright, aren't they?
Ten years isn't seeming nearly long enough anymore.