Code Review

What and Why

Code review is the practice of having one or more engineers read and comment on code changes before they're merged. It's the primary quality gate between "code that works on my machine" and "code that runs in production."

You encounter it in every professional engineering team: as a PR author waiting for review, and as a reviewer evaluating someone else's work. Both sides carry responsibility.

Code review catches bugs, yes — but that's not why teams invest in it. The deeper value:

• Knowledge propagation: reviewers learn what changed; authors get a second opinion on design.
• Shared ownership: no code is a black box known only to one person.
• Design feedback: "this will be painful to extend" is caught before it's merged.
• Team standards: code style and architectural decisions stay consistent across contributors.

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Core Concepts

What is a reviewer actually supposed to do?

This question has a surprisingly unclear answer in most teams. If your answer is "check for…