There are all kinds of things that I think I "should" know and don't. A few things that I don't understand as well as I'd like to:
- Database replication and sharding (seriously how does replication even work)
- How fast a computer can process data (should I expect more or less than 6GB/s if it's a simple CPU-bound program where the data is already in RAM?)
- How do system calls work, reeeeally? (I do not understand context switching nearly as well as I could!)
- An truly embarrassing amount of basic statistics, even though I have a math degree.
There are lots of much more embarrassing things that I just can't think of right now.
I've started trying to ask questions any time I don't understand something, instead of worrying about whether people will think I'm dumb for not knowing it. This is magical, because it means I can then learn those things!
One of my very favorite examples of this is how I started learning about operating systems. At the beginning of Hacker School, I realized that I legitimately did not know what a kernel was or did more than "er, operating system stuff".
This was super embarrassing! I'd been using Linux for 10 years, and I didn't really understand at all what the basic responsibilities of the Linux kernel were. Oh no! Instead of hiding under a rock, I asked. And then people told me, and I wrote What does the Linux kernel even do?.
I don't know how I would have learned without asking. Now I have given talks about getting started with understanding the Linux kernel! So fun!
One surprising thing about asking questions is that when I start digging into a problem, people who I respect and who know a lot will sometimes not know the answers at all! For instance, I'll think that someone totally knows about the Linux kernel, but of course they don't know everything, and if I'm trying to do something specific like write a rootkit they might not know all the details of how to do it.
aphyr is a really good example of someone who asks basic questions and gets unexpected answers. He does research into whether distributed systems are reliable (linearizable? consistent? / available?). The results he finds are like RabbitMQ might lose 40% of your data. Ooooops. If you don't start asking questions about how RabbitMQ works from the beginning (in his case, by writing a program called Jepsen that automates this kind of reliability testing), then you'll never find that out. (be skeptical! Don't believe what people say even if they're using fancy words!)
"I don't understand."
Another hard thing is admitting that I don't understand. I try to not be too judgemental about this -- if someone is explaining something to me and it doesn't make sense, it's possible that they're explaining it badly! Or that I'm tired! Or any other number of reasons. But if I don't tell them I'm don't understand, I'm never going to understand the damn thing.
So I try to take a deep breath and say cheerfully "Nope!", figure exactly which aspect of the thing I don't understand, and ask a clarifying question.
As a sideeffect, I've acquired much less patience and respect for people who give talks which sound really smart but are difficult to understand, and somewhat more willingness to ask questions like "so what IS <basic concept that you did not explain>?".
A difficult thing about asking questions is that I have to be pretty careful about asking the right questions and making it clear which parts I know already. This is just good hygiene, and makes sure nobody's time gets wasted.
For instance, I have sometimes said things like "I don't know anything about statistics", which is actually false and sometimes results in people trying to explain basic probability theory to me, or what an estimator is, or maybe the difference between a biased and unbiased estimator. It turns out these are actually things I know! So I need to be more specific, like "can we walk through some basic survival analysis?" (actually a thing I would like to understand!)
So! Understanding and learning are more important than feeling smart. Probably the most important thing I learned at Hacker School was how to ask questions and admit when I don't understand something. I know way more things now as a result! (see: this entire blog of things I have learned)