Beyond the Strangler Fig: Rapid UI Replacement for Faster ROI

The $3.6 trillion global technical debt isn't just a line item on a balance sheet; it is the primary bottleneck for enterprise innovation. For a decade, the "Strangler Fig" pattern has been the gold standard for migrating these monolithic systems. But in 2024, the Strangler Fig is failing. It’s too slow, too manual, and relies on documentation that 67% of legacy systems simply do not have.

TL;DR: While the Strangler Fig pattern works for back-end services, it is too slow for UI modernization; Visual Reverse Engineering via Replay allows teams to bypass "documentation archaeology" and modernize legacy interfaces 70% faster.

The Failure of Traditional Modernization Patterns#

The Strangler Fig pattern—incrementally replacing legacy functionality with new services—was designed for an era of stable, long-running server-side logic. When applied to the front-end, it hits a wall. Modernizing a legacy UI (think PowerBuilder, Delphi, or ancient JSP) using traditional methods requires an average of 40 hours of manual work per screen just to document the existing state.

Enterprise architects are finding that by the time they "strangle" the old UI, the "new" technology stack they chose at the start of the project is already nearing obsolescence. With 70% of legacy rewrites failing or exceeding their timelines, the "Big Bang" is a career-ender, and the "Strangler" is a slow bleed.

The Cost of Documentation Archaeology#

Most enterprises spend 30-40% of their modernization budget just trying to understand what the current system actually does. When documentation is missing, developers are forced into "archaeology"—reading obfuscated code or interviewing retired employees to map out business logic.

Moving Beyond the Strangler with Visual Reverse Engineering#

To move beyond the Strangler, we must decouple the "understanding" phase from the "coding" phase. This is where Visual Reverse Engineering changes the calculus. Instead of reading code to understand the UI, we record real user workflows.

Replay uses these recordings as the "source of truth." By capturing the actual interactions, state changes, and API calls of a legacy system in production, Replay generates documented React components and API contracts automatically. This shifts the timeline from 18 months of manual labor to weeks of automated extraction.

Why Video is the New Source of Truth#

In a regulated environment—be it Financial Services or Healthcare—the "as-is" state of a system is often different from the "as-intended" state in the original (and now lost) requirements.

1. •Precision: Video captures edge cases that developers miss during manual audits.
2. •Speed: Replay reduces the time spent per screen from 40 hours to just 4 hours.
3. •Logic Preservation: By observing the data flow during a recording, Replay’s AI Automation Suite identifies the underlying business logic that must be preserved in the modern React component.

💰 ROI Insight: For a 100-screen enterprise application, manual reverse engineering costs approximately $400,000 (based on $100/hr dev rates). Replay reduces this to $40,000—a 90% cost reduction on the discovery phase alone.

Technical Architecture: From Black Box to React#

When we talk about going beyond the Strangler, we are talking about a structured pipeline that converts legacy pixels into clean, maintainable code.

Step 1: Visual Capture#

A business analyst or end-user records a standard workflow (e.g., "Processing a Claim" or "Onboarding a New Client"). Replay captures the DOM structure (if web-based) or visual elements (if desktop-based), along with the network traffic.

Step 2: Component Extraction#

Replay’s Blueprints (Editor) analyzes the recording. It identifies repeating patterns—buttons, input fields, complex data tables—and maps them to a modern Design System.

Step 3: Logic Mapping#

The AI Automation Suite generates the necessary hooks and state management. It doesn't just copy the UI; it recreates the behavior.

typescript
// Example: Generated React component from Replay Visual Extraction
// Source: Legacy Insurance Claims Portal (Circa 2004)
// Extraction Date: 2024-05-20

import React, { useState, useEffect } from 'react';
import { Button, TextField, Alert } from '@acme-corp/design-system';
import { useClaimsProcessor } from '../hooks/useClaimsProcessor';

export const ClaimsEntryForm = ({ claimId }: { claimId: string }) => {
  const { data, loading, submitClaim } = useClaimsProcessor(claimId);
  const [formData, setFormData] = useState(data);

  // Business logic preserved from legacy system recording:
  // "If claim_type is 'Automotive', the deductible field must be non-zero."
  const validateLogic = (val: number) => {
    return formData.type === 'Automotive' && val <= 0;
  };

  return (
    <div className="p-6 space-y-4">
      <TextField 
        label="Claim Amount"
        value={formData.amount}
        onChange={(e) => setFormData({...formData, amount: e.target.value})}
        error={validateLogic(formData.amount)}
      />
      <Button 
        onClick={() => submitClaim(formData)}
        disabled={loading}
      >
        Process Claim
      </Button>
    </div>
  );
};

The Replay Feature Suite: Built for the Enterprise Architect#

Modernization isn't just about code generation; it's about governance and long-term maintainability. Replay is built for regulated industries where "move fast and break things" is not an option.

The Library (Design System Integration)#

Most legacy systems have inconsistent UI. Replay’s Library allows you to map legacy elements to your new, centralized Design System. As Replay extracts components, it automatically replaces the "ugly" legacy button with your brand-approved, accessible React component.

Flows (Architecture Visualization)#

One of the biggest risks in the Strangler Fig approach is losing track of the "Flow." Replay generates Flows—visual maps of how users move through the system. This provides an instant technical debt audit, showing which paths are most used and which are redundant.

Blueprints (The Editor)#

The Blueprints editor is where the "translation" happens. Architects can review the extracted logic, refine API contracts, and ensure that the generated code meets internal standards before it ever hits the repository.

⚠️ Warning: Do not attempt to modernize without a defined API strategy. Replay generates API Contracts from the legacy traffic, which should be used to build your backend shim or BFF (Backend for Frontend).

Implementation Roadmap: The 30-Day Modernization Pilot#

If you are facing an 18-month rewrite, you can validate the Beyond the Strangler approach in 30 days.

Phase 1: Selection (Week 1)#

Identify 5-10 high-impact, high-complexity screens. These are usually the ones that developers are afraid to touch because the original authors left the company years ago.

Phase 2: Recording & Extraction (Week 2)#

Record the workflows. Let Replay’s AI Automation Suite ingest the video and network logs. Generate the initial Library of components.

Phase 3: Refinement (Week 3)#

Use Blueprints to refine the generated React code. Align the output with your enterprise coding standards and security protocols (SOC2/HIPAA).

Phase 4: Integration (Week 4)#

Deploy the new UI components alongside the legacy system using a reverse proxy. The user sees a modern interface, while the legacy backend continues to process the data—achieving ROI in weeks instead of years.

💡 Pro Tip: Focus on "Read-Heavy" screens first. They are the easiest to extract and provide the fastest visual impact for stakeholders.

Addressing the Skepticism: Logic and Security#

When I speak to CTOs about Visual Reverse Engineering, the concerns are usually the same: "What about the hidden business logic?" and "Is it secure?"

Business Logic Preservation#

The Strangler Fig often fails because developers miss "invisible" logic—the weird validation rule hidden in a stored procedure or a legacy script. Because Replay records the actual data exchange between the UI and the server, it captures the outcomes of that logic. If the server rejects a specific input, Replay identifies that constraint and documents it in the API contract.

Security and Compliance#

For Healthcare and Financial Services, cloud-based AI is often a non-starter. Replay offers On-Premise deployment and is SOC2 and HIPAA-ready. Your source code and user data never leave your secure environment.

The Future of Enterprise Architecture#

The era of the "Big Bang" rewrite is over. The $3.6 trillion in technical debt cannot be cleared by manual labor alone. We need tools that understand existing systems as well as we understand new ones.

Replay represents a shift in philosophy. We are moving away from "archaeology" and toward "automated understanding." By going beyond the Strangler, we don't just replace old code; we reclaim the time and budget needed to build the future.

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Frequently Asked Questions#

How long does legacy extraction take with Replay?#

A typical complex enterprise screen takes approximately 40 hours to manually document, design, and code in React. With Replay, the recording takes minutes, and the extraction/refinement process takes about 4 hours. This represents a 90% reduction in time-to-code.

Does Replay work with desktop applications or just web?#

Replay is designed for the enterprise. While it excels at web-based legacy systems (JSP, ASP.NET, Angular.js), its visual extraction engine can be used to map workflows from desktop environments (Citrix, Delphi, PowerBuilder) into modern web components.

What about business logic preservation?#

Replay captures the interaction between the UI and the API. While it generates clean React code for the front-end, it also produces detailed API Contracts and documentation of the data transformations observed during the recording. This ensures that no "hidden" validation rules are lost during the migration.

Can we use our own Design System?#

Yes. Replay’s Library feature is designed to ingest your existing Figma tokens or React component library. During the extraction process, you can map legacy elements directly to your modern components, ensuring 100% brand consistency from day one.

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