Code Review Guide

Understand the code

Make sure you completely understand the code
Evaluate all the architecture tradeoffs

Check code quality

Verify code correctness
Check for well-organized and efficient core logic
Is the code as general as it needs to be, without being more general that it has to be?
Make sure the code is maintainable
Enforce stylistic consistency with the rest of the codebase

Verify that the code is tested well

Confirm adequate test coverage
Check tests having the right dependencies and are testing the right things

Make sure the code is safe to deploy

Ask if the code is forwards/backwards compatible. In particular, be on the lookout if the code is changing the serialization / deserialization of something
Run through a roll-back scenario to check for rollback safety

Check for any security holes and loop in the security team if you’re unsure

Answer: If this code breaks at 3am and you’re called to diagnose and fix this issue, will you be able to?