Why junior devs should review seniors’ commits

I've had very good experiences with reviewing complex changes with less experienced dudes. You have to approach it with a different mindset though.

With more experienced guys, I give them code and they fire back "Yo, those 10 things look bad, those 8 things are easy problems, those two things are probably broken, and you turned your brain off in that test".

Less experienced team members can be intimidated by code and standing and you have to overcome that. But I've had great experiences by handing them change sets, give them some time to read it until they are ready and comfortable to ask me questions about it and to tell me what it does, and then we just talk about the code.

This resulted in a really cool situation. I was working on a lock-free, cache friendly tree implementation in java and had relaxed a couple of locks and it was some really tough stuff. So we ended up talking about style, and then digressing into explanations of java memory visibility, concurrency, lock-free algorithms, several square meters of whiteboard painted over several times, and then this girl says "Yeah so if I get this right your code is slower than it could be, and wrong in a case. Let me show you". And she was right, and I was floored.

There are folks who are junior in their attitude and experience, but not in their coding or design skill set. I’m very senior, yet I’d say I suck at reviewing code. There are other things I’m good at, code reviews just aren’t one of those things. My best code reviewer on the team is a dude who’s just out of school. In fact, he’s probably the second best reviewer I’ve seen in 20 years in this industry, and the other dude is only better than him because he had incredibly deep knowledge of a gnarly problem domain specific to that particular team. Frankly, I’m shocked that someone who’s 22 years old can be this good, and I no longer believe there’s that huge of a gap in technical skill between junior and senior folks per se. I also think that people of such extreme skill should be paid at the same rate as the senior people even though they do not possess an illustrious resume quite yet. It pains me to see that he could be easily making three times as much if he only had “worked on such and such bullshit products for 10 years” on his resume. If I ever poach him, I’ll make sure he gets paid really well.

The main point is, just because someone is nominally “junior” means little to nothing in terms of their ability to write and review code. The advantage of experience is largely in knowing how to restrict the search space when solving any given problem.

A recurring theme I've seen is senior dev's not asking other devs for feedback. While it's obviously something that would be great for the junior dev, usually senior devs tend to prefer to be the reviewer, not the reviewee. But I think this is to their folly; and certainly inhibits any juniors on the team.

Besides code reviewing, it is useful to spend some time just to read and study commits made by other developers to observe and learn how they do things.