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Level 9 / Project 08 - Change Impact Analyzer

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— This project — — Flashcards — —

Focus

  • BFS graph traversal for impact propagation through service dependencies
  • Risk scoring with weighted factors (change type, service tier, dependency depth)
  • Service dependency graph modeling with tier classification
  • Blast radius estimation for proposed changes
  • Stakeholder identification from affected service ownership

Why this project exists

Before deploying a change, engineers must understand its blast radius: which services, teams, and SLOs are affected. A database schema migration might seem local, but it propagates through 12 downstream services owned by 4 different teams. This project builds an impact analyzer that traverses dependency graphs, scores change risk based on service tiers and change types, and identifies all affected stakeholders — the same analysis that platform teams perform before every production deployment.

Run (copy/paste)

cd <repo-root>/projects/level-9/08-change-impact-analyzer
python project.py --demo
pytest -q

Expected terminal output

{
  "change": {"service": "user-db", "type": "schema_migration"},
  "blast_radius": 5,
  "risk_score": 8.5,
  "affected_services": [...],
  "affected_teams": [...]
}
7 passed

Expected artifacts

  • Console JSON output with impact analysis
  • Passing tests
  • Updated notes.md

Alter it (required)

  1. Add a visualize_blast_radius() method that outputs affected services as a tree diagram.
  2. Add a ChangeType.INFRASTRUCTURE variant with its own risk scoring multiplier.
  3. Add a --team filter that shows only impact on services owned by a specific team.

Break it (required)

  1. Create a circular dependency (A -> B -> A) — does transitive_dependents handle cycles?
  2. Analyze a change to a service not in the graph — what error or result occurs?
  3. Set service tier to 0 (invalid) — does the risk scoring handle it?

Fix it (required)

  1. Add cycle detection in transitive_dependents using a visited set.
  2. Return a clear error when the changed service is not found in the graph.
  3. Validate service tier values are in the range 1-3.

Explain it (teach-back)

  1. What is blast radius analysis and why is it important before making changes?
  2. How does BFS traversal find transitive dependents in a service graph?
  3. Why do schema changes carry higher risk than code changes?
  4. How do real organizations use impact analysis to decide deployment strategies?

Mastery check

You can move on when you can: - explain BFS graph traversal and how it maps to dependency discovery, - add a new service to the graph and predict its impact on risk scores, - describe how service tiers affect risk scoring (tier-1 = critical = higher risk), - design an impact analysis for a real microservices architecture.

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