The Architect’s Framework for Prioritizing Legacy Modules for Extraction

The $3.6 trillion global technical debt is not a management problem; it is an architectural failure. For decades, Enterprise Architects have been trapped in a cycle of "Big Bang" rewrites that consume 18 to 24 months of capital only to result in a 70% failure rate. The industry has been operating on a lie: that you must understand a legacy system's ancient, undocumented codebase before you can modernize it.

The reality is that 67% of legacy systems lack any meaningful documentation. Manual "code archaeology"—the process of developers digging through COBOL, monolithic Java, or legacy .NET—is a waste of high-value engineering talent. It takes an average of 40 hours to manually document and reconstruct a single complex legacy screen.

The future isn't rewriting from scratch; it’s understanding what you already have through Visual Reverse Engineering. This Architect Framework for Prioritizing Legacy Modules provides a data-driven path to move from a black box to a documented, modern React codebase in days, not years.

TL;DR: Stop guessing which modules to rewrite; use a visual-first framework to record user workflows, extract business logic via Replay, and prioritize extraction based on "Value-to-Volatility" scores to achieve 70% time savings.

The Failure of Traditional Modernization Approaches#

Most enterprise modernization projects fail because they treat the legacy system as a monolith that must be replaced in one Herculean effort. This "Big Bang" approach introduces catastrophic risk to regulated environments in Financial Services, Healthcare, and Government.

Traditional "archaeology" requires developers to spend weeks tracing spaghetti code to find business rules. When you use Replay, you bypass the code entirely and use the video as the source of truth. By recording a real user workflow, Replay’s AI Automation Suite extracts the underlying logic, API contracts, and UI components automatically.

The Architect’s Framework for Prioritizing Modules#

To modernize effectively, you need a scoring mechanism. You cannot extract everything at once. You must identify the "High-Value, Low-Complexity" targets that provide immediate ROI.

Phase 1: The Visual Inventory#

Before you can prioritize, you must see. Use Replay to record the core workflows of your legacy application. This creates a "Flow" map—a visual architecture of how users actually interact with the system, rather than how the 15-year-old documentation says they do.

💰 ROI Insight: Manual documentation takes ~40 hours per screen. Replay reduces this to 4 hours by generating documentation and React components directly from recorded user sessions.

Phase 2: The V-V Scoring Matrix (Value vs. Volatility)#

Score every module from 1-10 on two axes:

1. •Business Value: How critical is this screen to revenue or compliance?
2. •Volatility: How often does the logic change? High volatility in a legacy system is a recipe for technical debt.

The Priority Tiers:

• •Tier 1 (High Value, High Volatility): Immediate candidates for Replay extraction. These are the bottlenecks.
• •Tier 2 (High Value, Low Volatility): Extract to stabilize and document.
• •Tier 3 (Low Value, High Volatility): Candidates for deprecation.
• •Tier 4 (Low Value, Low Volatility): Leave as-is (The "Maintenance" zone).

Step-by-Step: The Extraction Workflow#

Once you have identified a Tier 1 module, follow this technical framework to move from legacy to React.

Step 1: Recording and Observation#

A subject matter expert (SME) performs the workflow in the legacy application while Replay records the session. This isn't just a screen recording; it is a capture of the DOM, network requests, and state transitions.

Step 2: Visual Reverse Engineering#

Replay’s engine analyzes the recording to identify patterns. It maps the legacy UI to your modern Design System (The Library). If a button is clicked in the legacy app, Replay identifies the associated API call and the data structure returned.

Step 3: Generating the Modern Component#

Replay generates a clean, documented React component. Unlike generic AI code generators, this is built from the actual execution path of your legacy system.

typescript
// Example: Generated React component from Replay Visual Extraction
// Source: Legacy "Claims Processing" Screen #402
import React, { useState, useEffect } from 'react';
import { Button, TextField, Alert } from '@enterprise/design-system';
import { useClaimsAPI } from '../hooks/useClaimsAPI';

export function ClaimsAdjustmentModule({ claimId }: { claimId: string }) {
  const { data, loading, error, updateClaim } = useClaimsAPI(claimId);
  const [adjustmentAmount, setAdjustmentAmount] = useState<number>(0);

  // Business Logic extracted from Legacy Event Handler:
  // "If claim_status is 'PENDING' and adjust_val > 5000, require Manager Auth"
  const handleSubmission = async () => {
    if (data?.status === 'PENDING' && adjustmentAmount > 5000) {
      return Alert.show("Manager Authorization Required");
    }
    await updateClaim({ id: claimId, amount: adjustmentAmount });
  };

  if (loading) return <Spinner />;

  return (
    <div className="p-6 border-l-4 border-blue-500">
      <h3>Adjustment for Claim: {claimId}</h3>
      <TextField 
        label="Adjustment Amount"
        type="number"
        onChange={(e) => setAdjustmentAmount(Number(e.target.value))}
      />
      <Button onClick={handleSubmission}>Process Adjustment</Button>
    </div>
  );
}

Step 4: API Contract Extraction#

One of the biggest pain points in modernization is the "Black Box" API. Replay automatically generates OpenAPI/Swagger specifications based on the traffic recorded during the session.

yaml
# Generated API Contract from Replay Extraction
paths:
  /api/v1/claims/adjust:
    post:
      summary: "Extracted from Legacy Claims Module"
      parameters:
        - name: "claim_id"
          in: "body"
          required: true
          schema:
            type: "string"
      responses:
        200:
          description: "Adjustment Processed"
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/AdjustmentResponse'

Addressing the Technical Debt Audit#

Before committing to an extraction, you must perform a Technical Debt Audit. Most organizations are flying blind, unaware that they are spending 80% of their budget on maintaining the "Tail" of legacy systems.

⚠️ Warning: Proceeding with a rewrite without an automated technical debt audit usually leads to "feature parity" traps where you spend 6 months rebuilding features that no one actually uses.

Replay identifies "Dead Workflows"—screens and modules that are present in the code but never appear in user recordings. By eliminating these during the prioritization phase, you can reduce the scope of your modernization by up to 30%.

Security and Compliance in Regulated Industries#

For Financial Services and Healthcare, "Cloud-only" is often a dealbreaker. Replay is built for these environments:

• •SOC2 & HIPAA Ready: Data handling meets the highest security standards.
• •On-Premise Availability: Keep your extraction engine within your own firewall.
• •PII Masking: Automatically redact sensitive user data during the recording and extraction process.

Why Visual Reverse Engineering Beats Manual Refactoring#

Manual refactoring is a linear process:

. If any step fails, the whole chain breaks.

Visual Reverse Engineering with Replay is a parallel process. Because the "Video is the Source of Truth," you are documenting and coding simultaneously. The "Blueprints" (Editor) allow architects to tweak the generated React components in real-time, ensuring they align with the new architecture while preserving the legacy business logic.

📝 Note: Replay doesn't just give you code; it gives you an E2E test suite. Because it knows what the "Success" state looked like in the legacy system, it generates Playwright or Cypress tests to ensure the new component behaves exactly like the old one.

The Comparison of Effort#

Frequently Asked Questions#

How long does legacy extraction take?#

Using the Replay framework, a standard enterprise module (3-5 complex screens) can be fully extracted, documented, and converted into functional React components in 2 to 5 days. This compares to the 4-6 weeks required for manual reconstruction.

What about business logic preservation?#

This is the core strength of Replay. By recording the actual execution of the legacy system, we capture the "hidden" logic—the edge cases that aren't in the documentation. Replay's AI Automation Suite analyzes the state changes during the recording to ensure the generated TypeScript logic matches the legacy behavior 1:1.

Does Replay support mainframe or green-screen apps?#

Yes. If a user can access it through a terminal emulator or a web-wrapped interface, Replay can record the workflow and extract the logic. We transform the visual output into structured data, allowing you to move from "Green Screen" to "React" without needing a COBOL expert.

How does this handle technical debt?#

Replay provides a Technical Debt Audit by identifying unused code paths and redundant modules. By focusing only on the workflows that users actually perform, you "right-size" your application during the extraction process, effectively cleaning up years of debt in a single pass.

The Architect’s Mandate#

The role of the Enterprise Architect is changing. You are no longer the "Gatekeeper of the Monolith"; you must become the "Engine of Modernization."

Stop the 18-month rewrite cycles. Stop the manual archaeology. Use the Replay framework to prioritize your modules, record your workflows, and extract your future. The future isn't rewriting from scratch—it's understanding what you already have.

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