Module 4: CI/CD Pipelines & Release Engineering: Mistake Clinic

This clinic turns wrong moves into reusable judgment. Use it after each practice page and again before the quiz or checkpoint.

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Module-Specific Mistake Radar

Start with these traps. Replace or extend them with real mistakes from your own work.

Mistake to look for	Where it shows up	Symptom	Repair evidence
Finishing Pipeline Design Lab with only a final answer	Pipeline Design Lab	The work has no failed case, trace, test, proof gap, or design stress point.	Add the smallest broken example and show the repair that changes the result.
Finishing Deployment Strategy Workshop with only a final answer	Deployment Strategy Workshop	The work has no failed case, trace, test, proof gap, or design stress point.	Add the smallest broken example and show the repair that changes the result.
Finishing Release and Migration Clinic with only a final answer	Release and Migration Clinic	The work has no failed case, trace, test, proof gap, or design stress point.	Add the smallest broken example and show the repair that changes the result.
Finishing CI/CD Katas with only a final answer	CI/CD Katas	The work has no failed case, trace, test, proof gap, or design stress point.	Add the smallest broken example and show the repair that changes the result.
Treating The Goal: Small, Frequent, Reversible Changes as vocabulary instead of a tool	The Goal: Small, Frequent, Reversible Changes	The explanation names the concept but cannot decide between two cases.	Write one example, one non-example, and the rule that separates them.
Treating Trunk-Based Development vs GitFlow as vocabulary instead of a tool	Trunk-Based Development vs GitFlow	The explanation names the concept but cannot decide between two cases.	Write one example, one non-example, and the rule that separates them.

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Practice Mistake Checks

Pull any miss from these checks into your mistake log.

Pipeline Design Lab

Source: practice/01-pipeline-design-lab.md

For each, identify the error:

1. "We rebuild the image in every environment to keep it fresh."
2. "Our CI is fast -- we skip unit tests and rely on integration tests."
3. "We tag staging and prod as separate images."
4. "We retry flaky tests three times to keep the pipeline green."
5. "actions/checkout@v4 is fine because it's maintained by GitHub."

Deployment Strategy Workshop

Source: practice/02-deployment-strategy-workshop.md

For each, identify the error:

1. "Our rollback plan is to revert the PR and redeploy."
2. "We don't need rollback -- we only deploy good code."
3. "Canary with 10 pods means we just watch the first pod."
4. "Blue-green is always safer than rolling."
5. "We flipped the flag at 100% last week; we'll remove it next quarter."

Release and Migration Clinic

Source: practice/03-release-and-migration-clinic.md

For each, identify the error:

1. "We ship the code change and the column drop in the same commit."
2. "This release is v2.3.0 -- we renamed an endpoint but it's backward compatible because old clients can still call it."
3. "We run migrations in the app's startup so it's always up-to-date."
4. "We sign images with a key committed to the repo so CI can use it."
5. "The tag v1.2.3 in our registry -- I updated it last week."

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Repair Protocol

For each real mistake:

1. Reproduce the failure on the smallest example, trace, proof, query, command, or design sketch.
2. Name the hidden assumption.
3. Repair the artifact.
4. Save evidence that changed: failing then passing test, corrected proof step, revised diagram, safer command, benchmark, or review note.
5. Add one retrieval card beginning with Check... before... or Do not use... when....

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Mistake Log

Date	Mistake	Symptom	Root cause	Repair evidence	Retrieval card
Starter	Pick one radar row above	Explain how it would fail in this module	Name the assumption	Add a counterexample or corrected artifact	Write the card before closing the page

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Completion Standard

• At least five real mistakes are logged.
• At least two mistakes include a counterexample or failing test.
• At least one mistake connects to an older semester skill.
• At least one correction changes code, a proof, a diagram, a command transcript, a query, or a design decision.