5.5Code review and interpreting sequence diagrams

Automation is not write-once but the practice of a team changing it safely over time. Two practices for that are this section's theme. One is code review—a mechanism where a third party reads a change before it enters production to check bugs, readability, and security. The other is reading a sequence diagram—the ability to grasp from a diagram in what order and what several components (client, API, auth server) exchange. Both are learned not as memorization but as material for interpreting a given review situation or diagram and judging the next move.

5.5.1Code-review principles and benefits

• The aims of review are early bug detection, readability/maintainability, security, and knowledge sharing. Having a third party read a change before production catches hardcoded plaintext passwords, dangerous deletions, and missed boundary conditions before release. It also strongly prevents siloed knowledge and shares design intent across the team.
• Good review practice: keep PRs small (smaller diffs mean fewer misses), focus on correctness, readability, and security, and comment constructively on the code, not the person. Comments should be specific and grounded, ideally with a suggested fix. Layering human review on top of passing CI automated checks (lint/tests) is efficient.