1-1: The Product Debt Index (PDI)
Learn the exact framework used in $7,500 advisory engagements to value legacy codebases.
🎯 What You'll Learn
- ✓ Define the Innovation Tax
- ✓ Calculate Technical Insolvency
- ✓ Build a PDI equation
- ✓ Defend refactoring budgets to the board
Lesson 1: The Innovation Tax
Code doesn't rot, but your architecture’s fitness function decays. The Innovation Tax is the percentage of total engineering capacity spent solely on fighting legacy constraints instead of shipping new value. If your tax exceeds 40%, you are technically insolvent.
Maintenance hours / Total engineering hours × 100
The point where maintenance costs exceed the revenue generated by new features.
Never say "tech debt" to a CFO. Call it an "unfunded capital liability."
Calculate your team's current Innovation Tax over the last three sprints using Jira/Linear telemetry.
Lesson 2: Calculating the PDI
The Product Debt Index is a deterministic equation. PDI = (Cost of Delay × Dependency Graph Depth) / Automated Coverage %. A PDI > 100 means you have a systemic collapse risk.
Number of internal systems that must update for a single feature release.
Not just unit tests, but integration tests covering critical user flows.
Lost monthly revenue for a feature blocked by tech debt.
Select your most brittle service. Run the PDI equation against it and document the exact score.
Lesson 3: The Refactoring Strategy
You cannot halt the roadmap to rewrite the monolith. You must implement the Strangler Fig pattern, siphoning traffic bit by bit. This lesson covers the exact API gateway architecture needed to route legacy traffic to rewritten microservices.
A perimeter gateway routing traffic by bounded context.
Mirroring reads to the new service before cutting over writes.
The defect parity threshold required to decommission the legacy route.
Draw an architecture diagram showing the Strangler Fig proxy for your largest legacy domain.
Continue Learning: Track 1 - CTO / Engineering Leader
2 more lessons with actionable playbooks, executive dashboards, and engineering architecture.
Access Execution Fidelity.
You've seen the theory. The Vault contains the exact board-ready financial models, autonomous AI orchestration codes, and executive action playbooks that drive 8-figure valuation impacts.
Executive Dashboards
Generate deterministic, board-ready financial artifacts to justify CAPEX workflows immediately to your CFO.
Defensible Economics
Replace heuristic guesswork with hard mathematical frameworks for build-vs-buy and SLA penalty negotiations.
3-Step Playbooks
Actionable remediation templates attached to every module to neutralize friction and drive instant deployment velocity.
Engineering Intelligence Awaiting Extraction
No generic advice. No filler. Just uncompromising architectural truths and unit economic calculators.
Vault Terminal Locked
Awaiting authorization clearance. Access the module to decrypt architectural playbooks, P&L models, and deterministic diagnostic utilities.
Module Syllabus
Lesson 1: Lesson 1: The Innovation Tax
Code doesn't rot, but your architecture’s fitness function decays. The Innovation Tax is the percentage of total engineering capacity spent solely on fighting legacy constraints instead of shipping new value. If your tax exceeds 40%, you are technically insolvent.
Lesson 2: Lesson 2: Calculating the PDI
The Product Debt Index is a deterministic equation. PDI = (Cost of Delay × Dependency Graph Depth) / Automated Coverage %. A PDI > 100 means you have a systemic collapse risk.
Lesson 3: Lesson 3: The Refactoring Strategy
You cannot halt the roadmap to rewrite the monolith. You must implement the Strangler Fig pattern, siphoning traffic bit by bit. This lesson covers the exact API gateway architecture needed to route legacy traffic to rewritten microservices.
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The AI Economist: Leading Product Strategy When Build Costs Approach Zero
When generative AI collapses the cost of writing software toward zero, developer bandwidth ceases to be the constraint. The product bottleneck shifts from managing backlog velocity to managing uncertainty, evaluating system architecture efficiency, and preserving unit margins as a Product Economist.
Want to apply this to your organization with The Product Debt Index (PDI)?
Run a free diagnostic first. If the numbers concern you, book a session to build a remediation plan.
Richard Ewing: AI Economist & Capital Auditor