The Legacy Triage Framework: Deciding Which Modules to Extract, Maintain, or Kill

The average enterprise spends 80% of its IT budget just keeping the lights on. This "legacy tax" isn't just a line item; it’s a silent killer of innovation. When you’re staring at a $3.6 trillion global technical debt mountain, the instinct is often a "Big Bang" rewrite—an approach that fails 70% of the time.

The problem isn't the legacy code itself; it’s the lack of a strategic framework to handle it. You cannot treat a mission-critical billing engine the same way you treat a deprecated reporting module. You need The Legacy Triage.

TL;DR: The Legacy Triage is a strategic framework for categorizing legacy modules into four actions—Extract, Maintain, Kill, or Encapsulate—allowing teams to modernize high-value components in weeks rather than years using visual reverse engineering.

The Cost of Indecision#

Every year you delay a modernization decision, your technical debt accrues interest. In regulated industries like Financial Services and Healthcare, this debt manifests as security vulnerabilities and compliance risks. Most CTOs fall into the trap of "archaeology"—spending months manually documenting systems that no one understands.

Manual documentation takes an average of 40 hours per screen. For a standard enterprise application with 200 screens, that’s 8,000 hours of senior engineering time wasted on discovery before a single modern component is built.

The Legacy Triage Quadrant#

To execute a successful modernization, you must map every module in your system against two axes: Business Value and Technical Fragility.

1. Extract (High Value, High Fragility)#

These are your "Black Boxes." They contain critical business logic but are impossible to update without breaking dependencies. These are the primary candidates for Replay. Instead of manual reverse engineering, you record user workflows to extract documented React components and API contracts.

2. Maintain (High Value, Low Fragility)#

If it isn't broken and it’s delivering value, leave it. These modules should be wrapped in modern APIs but don't require a full UI overhaul yet.

3. Kill (Low Value, High Fragility)#

Enterprises are littered with "ghost modules"—features built for a single client in 2014 that are no longer used. The best way to modernize these is to delete them.

4. Encapsulate (Low Value, Low Fragility)#

These are utility functions or back-office tools that work fine. Move them to a container, put them on cheaper infrastructure, and stop thinking about them.

💰 ROI Insight: By killing the bottom 20% of unused legacy modules, organizations typically see a 15% immediate reduction in maintenance overhead and a significant decrease in the attack surface for security vulnerabilities.

---

Implementing the Triage: A Step-by-Step Guide#

Step 1: Automated Discovery and Recording#

Stop looking for the original documentation; it’s either missing or wrong (67% of legacy systems lack accurate docs). Use Replay to record real user workflows. This creates a "Video as Source of Truth." By capturing the actual state changes and network calls in the legacy environment, you bypass the "archaeology" phase entirely.

Step 2: Component Extraction#

Once a workflow is recorded, the triage moves to extraction. You aren't just taking screenshots; you are generating functional, typed code.

typescript
// Example: Legacy Component Extracted via Replay
// Original: Obscure JSP/Silverlight logic
// Result: Clean, Documented React Component

import React, { useState, useEffect } from 'react';
import { Button, TextField, Alert } from '@/components/ui'; // From your Replay Library
import { validateClaimSchema } from './schemas';

interface ClaimProcessorProps {
  claimId: string;
  initialData: any;
}

export const ClaimProcessor: React.FC<ClaimProcessorProps> = ({ claimId, initialData }) => {
  const [status, setStatus] = useState<'idle' | 'processing' | 'success'>('idle');
  
  // Replay preserved this business logic from the recorded trace
  const handleValidation = async (values: any) => {
    const isValid = await validateClaimSchema(values);
    if (isValid) {
      // Logic extracted from legacy XHR intercept
      processLegacyQueue(claimId, values);
    }
  };

  return (
    <div className="p-6 border rounded-lg shadow-sm">
      <h2 className="text-xl font-bold mb-4">Adjuster Portal: Claim {claimId}</h2>
      <TextField 
        label="Adjustment Amount" 
        defaultValue={initialData.amount}
        onChange={(v) => console.log(v)}
      />
      <Button 
        onClick={handleValidation}
        variant={status === 'processing' ? 'loading' : 'default'}
      >
        Submit to Legacy Core
      </Button>
    </div>
  );
};

Step 3: API Contract Generation#

The biggest hurdle in legacy triage is the "Black Box" API. Replay automatically generates API contracts by observing the traffic during the recording. This allows you to build a modern frontend that communicates perfectly with a legacy backend while you gradually migrate the services.

⚠️ Warning: Never attempt to rewrite the database schema and the UI at the same time. This is the #1 reason for the 18-month "death march" rewrite. Extract the UI first, then use the generated API contracts to refactor the backend.

---

Why "Big Bang" Rewrites Fail Technical Decision Makers#

The "Big Bang" approach assumes you can freeze the business for 18 months. You can't. While your team is busy rebuilding what you already have, your competitors are shipping new features.

The Replay approach changes the math:

• •Manual Extraction: 40 hours/screen
• •Replay Extraction: 4 hours/screen
• •Time Savings: 90% per component

For a 50-screen application, manual effort takes ~2,000 hours (roughly 1 year for one dev). With Replay, that same surface area is documented and extracted in 200 hours (5 weeks).

Handling Regulated Environments#

In Financial Services and Healthcare, "cloud-only" isn't always an option. Legacy triage often happens within the perimeter. Replay is built for this, offering SOC2 compliance, HIPAA-ready data handling, and On-Premise deployment options. You can record workflows in your secure environment without data ever leaving your network.

💡 Pro Tip: When triaging, look for "UI Consistency Debt." Use Replay’s Library feature to map extracted components directly to your modern Design System. This ensures that the modernized "Extract" modules don't just work better—they look and feel like part of a unified ecosystem.

---

The Technical Debt Audit#

Before committing to a triage path, perform a Technical Debt Audit. Replay automates this by analyzing the complexity of recorded flows.

1. •Cyclomatic Complexity: How many branching paths exist in the legacy UI?
2. •Data Dependency: How many external APIs does this screen touch?
3. •State Mutation: How often does the UI change state without a page reload?

If a module has high complexity and high data dependency, it is a "Must Extract." If it has low complexity and is rarely used, it is a "Kill."

typescript
// Example: E2E Test Generated from Replay Trace
// This ensures that the "Extracted" component matches 
// legacy behavior 1:1 before it goes to production.

describe('Legacy Workflow Validation', () => {
  it('should match legacy state transition for Claim Approval', () => {
    cy.visit('/modernized-claim-portal');
    cy.get('[data-testid="amount-input"]').type('5000');
    cy.get('[data-testid="submit-btn"]').click();
    
    // The assertion is based on the original recorded Replay trace
    cy.intercept('POST', '**/api/legacy/v1/process').as('legacyCall');
    cy.wait('@legacyCall').its('request.body').should('deep.equal', {
      id: '12345',
      amount: 5000,
      source: 'REPLAY_EXTRACTED_UI'
    });
  });
});

---

Frequently Asked Questions#

How does Replay handle complex business logic hidden in legacy code?#

Replay doesn't just "scrape" the UI. It records the underlying state changes and network interactions. By observing how the legacy system responds to specific inputs, Replay can generate documentation and code that mirrors the original business logic, even if the original source code is a mess of "spaghetti" logic.

Can we use this for systems with no source code available?#

Yes. This is the core value of Visual Reverse Engineering. Since Replay works by recording the execution of the application in the browser, it doesn't matter if the backend is COBOL, Java, or .NET. If it renders in a browser, we can extract it.

What is the typical learning curve for an architect?#

Most Enterprise Architects are up and running with Replay in a single afternoon. The platform is designed to fit into existing CI/CD pipelines and works with standard modern stacks like React, TypeScript, and Playwright.

How does this affect our SOC2/Compliance posture?#

Replay is built for regulated industries. We offer an on-premise version where all recording, extraction, and code generation happen within your VPC. No sensitive PII (Personally Identifiable Information) ever needs to touch our servers.

---

The Future Isn't Rewriting—It's Understanding#

The $3.6 trillion technical debt problem won't be solved by more developers writing more code from scratch. It will be solved by better understanding the code we already have.

The Legacy Triage framework, powered by Replay, allows you to stop guessing and start extracting. You can move from "Black Box" to a documented, modern codebase in days, not years. You save 70% of the time usually lost to manual discovery, and you eliminate the risk of the "Big Bang" failure.

---

Ready to modernize without rewriting? Book a pilot with Replay - see your legacy screen extracted live during the call.