**Myth:** You need to understand every line of code in your codebase to be a "real" developer.

Myth: You need to understand every line of code in your codebase to be a "real" developer.

Reality: Nobody understands the whole thing. Not even the people who wrote it. We're all just really good at pretending.

Last Tuesday, I watched a senior developer spend three hours explaining a system he built six months ago. By hour two, he was taking notes. His own notes. On his own code. At one point he said "oh, that's clever" and then immediately looked terrified because he didn't remember being that clever.

The codebase I'm working on has 847,000 lines. I've read maybe 12,000 of them. The rest is held together by what I call "architectural faith" and what my coworker calls "please don't break, please don't break, please don't break."

Here's what actually works: pick a 500-line radius around whatever you're changing. Understand that. Change it. Run the tests. If the tests pass, ship it. If they fail, blame the person who wrote the tests. (It's probably you from last year. That person was an idiot.)

The senior developers who seem to know everything? They're just better at pattern recognition. They've seen the same bug in eight different forms, so when version nine shows up, they recognize the shape. It's not omniscience - it's scar tissue from previous code battles.

I keep a file called "spooky_action_at_a_distance.txt" where I document things that break for reasons that make no sense. Like how changing the font size on a button once broke the login form. Or how adding a comment caused a memory leak. (The comment was "this should not cause a memory leak.")