Defend your system

Overview

Module	iv.01 · proof · docs · Pass 11 · 1 to 2 h
You build	a written review with supporting evidence
Tests	course/solve/iv.01 (q1 is self-graded against course/rubrics/design-review.md)
Needs	none
Used by	no code call site; this is an independent artifact
Milestone	MS-P11

Key Takeaways

• Tie each claim to the exact platform evidence that Defend your system produces.
• State the owner, success condition, and recovery action before declaring the work complete.
• Record unresolved assumptions so the next review can test them.

How to work this chapter

ol start iv.01
ol tests iv.01
ol check iv.01

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1. Why now

A technical defense tests whether you understand the system you built and can explain its limits to another engineer.

2. Principles

Answer from evidence. State the constraints, rejected alternatives, failure behavior, and a number you can reproduce. Admit when data is unavailable and name how you would obtain it.

3. Worked example

Defend why the engine and gateway use separate HTTP and gRPC boundaries. Describe how a rolling API migration behaves during a worker restart, then calculate one capacity limit from the design.

4. Claim and rubric

Write docs/defense/answers.md as the worked reflection or design review. Answer each line of course/rubrics/design-review.md with evidence from the completed system, then self-grade q1; each no becomes a review note with an owner and next step. The check verifies the artifact and records the rubric self-grade.

5. Pitfalls

#	Pitfall	Symptom	Caught by
1	Treating version selection or a document claim as implicit	A reader or client cannot determine which contract or evidence applies.	artifact and rubric self-grade
2	Skipping the failure path	The successful example works, but malformed input or rollback breaks the system.	artifact and rubric self-grade
3	Omitting a named owner and recovery condition	The artifact cannot guide an operator when conditions change.	artifact and rubric self-grade

6. Where it’s used next

Direction	Module	Connection
Back	review.03	Read this declared prerequisite before producing the artifact; use it to verify the relevant contract or evidence.
Back	field.07	Read this declared prerequisite before producing the artifact; use it to verify the relevant contract or evidence.

Going further

Resource	What to inspect
Course system contract	Use the current contracts and system boundaries as evidence when defending this review.