Maintenance & Tech Debt

Segments: MTD Mechanics

Segment 1: Software Evolution & Maintenance

• Lehman’s Laws of Software Evolution
• Maintenance Types: Corrective, Adaptive, Perfective, Preventive
• The Software Aging Process

Segment 2: Technical Debt Fundamentals

• The Ward Cunningham Metaphor
• Debt Types: Deliberate vs. Inadvertent
• Interest, Principal, and the Cost of Delay

Segment 3: Tech Debt Quantification

• Static Analysis and Complexity Metrics
• SQALE Method and Technical Debt Ratio
• Impact Analysis on Velocity and Quality

Segment 4: Legacy System Modernization

• Strategies: Rewrite, Re-architect, Encapsulate
• The Strangler Fig Pattern
• Migration Risk Management

Segment 5: Refactoring Mechanics

• Code Smells and Antipatterns
• Boy Scout Rule & Continuous Refactoring
• Automated Refactoring Tools and Techniques

Segment segmental 6: Testing in Maintenance

• Retaining Invariants during Restoration
• Characterization Testing (Golden Master)
• Regression Suite Optimization

Segment 7: Maintenance Management

• Managing Stakeholder Expectations
• Balancing Feature Work vs. Debt Repayment
• Documentation Recovery and Knowledge Transfer

Segment 8: Advanced Evolution

• Evolutionary Architecture Dynamics
• Fitness Functions for Structural Integrity
• System Archeology and Impact Mapping

Segment 9: Case Studies

• Decomposing Monolithic Enterprise Systems
• Refactoring High-Scale Legacy Platforms
• Modernizing Mission-Critical Real-time Systems

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Learning Map: Evolution Progression

1. Stage 1: Fundamentals (Weight: 1)
   • Maintenance Types and Software Evolution Laws.
2. Stage 2: Quantification (Weight: 2)
   • Tech Debt Metrics and Impact Assessment.
3. Stage 3: Strategy (Weight: 3)
   • Modernization Patterns (Strangler Fig).
4. Stage 4: Tactics (Weight: 4)
   • Refactoring Mechanics and Testing Invariants.
5. Stage 5: Optimization (Weight: 5)
   • Evolutionary Architecture and Long-term Health.

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In-Scope / Out-of-Scope

• In-Scope: Evolution theory, debt metrics, refactoring patterns, and modernization strategies.
• Out-of-Scope: Pure DevOps automation (Pillar 05), new system architecture (Pillar 03).

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Technical Pointers

• Pillar SE (09-03): Design patterns for extensibility.
• Pillar SRE (07-05): Reliability constraints during migration.