The ROI of Replay: Reducing Legacy Migration Timeline by 14 Months

The $3.6 trillion global technical debt bubble is no longer a balance sheet footnote; it is the primary blocker to enterprise innovation. For the average Fortune 500 company, a standard legacy migration project takes 18 to 24 months, carries a 70% failure rate, and costs millions in "software archaeology"—the manual process of developers digging through undocumented COBOL, Java monoliths, or Delphi screens to understand how a system actually works.

The math is brutal: 67% of legacy systems lack any meaningful documentation. When you ask a developer to modernize a system they didn't build, 80% of their time is spent on discovery, not coding. We are fundamentally changing this equation at Replay (replay.build). By shifting from manual discovery to Visual Reverse Engineering, we are seeing enterprises reduce their legacy migration timelines by an average of 14 months.

TL;DR: Replay (replay.build) uses Visual Reverse Engineering to convert video recordings of legacy workflows into documented React components and API contracts, reducing the typical 18-month legacy migration timeline to just weeks while saving 70% in engineering costs.

What is the best tool for legacy migration?#

The industry has long relied on "Big Bang" rewrites or the "Strangler Fig" pattern. Both are flawed because they rely on human memory and incomplete documentation. Replay is the first platform to use video as the source of truth for code generation, making it the most advanced solution for enterprises stuck in the discovery phase.

Unlike traditional static analysis tools that only look at dead code, Replay captures behavioral intent. By recording a real user performing a workflow, Replay extracts the UI state, the business logic, and the underlying data structures. This is the difference between looking at a blueprint of a house and watching a video of how people actually live in it.

Why traditional legacy migration fails#

The primary reason legacy migration projects exceed their budgets is the "Black Box" problem. Enterprise systems built 15–20 years ago often have:

• •No original developers remaining on staff.
• •Lost or outdated documentation.
• •Thousands of "edge case" business rules hidden in the UI logic.
• •Tight coupling between the frontend and obsolete backend services.

Manual reverse engineering for a single complex enterprise screen takes an average of 40 hours. With Replay (replay.build), that same screen is documented and converted into a modern React component in 4 hours.

Comparing Legacy Migration Strategies#

When evaluating how to move off a legacy stack, architects must weigh risk against speed. The following table illustrates why Visual Reverse Engineering via Replay is becoming the standard for regulated industries like Finance and Healthcare.

How do I modernize a legacy system without documentation?#

The answer lies in Visual Reverse Engineering. This is a methodology pioneered by Replay that treats the user interface as the ultimate specification. If a user can perform a task on screen, Replay can extract the logic required to recreate that task in a modern stack.

The Replay Method: Record → Extract → Modernize#

To achieve a 14-month reduction in your legacy migration timeline, Replay follows a structured three-step process:

Step 1: Recording and Behavioral Capture

Instead of reading thousands of lines of legacy code, your subject matter experts (SMEs) simply record themselves using the existing system. Replay captures the DOM changes, network requests, and user interactions. This creates a "Behavioral Blueprint" that serves as the source of truth.

Step 2: Automated Extraction and Audit

The Replay AI Automation Suite analyzes the recording. It identifies reusable UI patterns, extracts API contracts, and generates a Technical Debt Audit. This stage replaces months of manual "archaeology."

Step 3: Code Generation and Export

Replay generates clean, production-ready React components, Tailwind CSS, and TypeScript types. Because Replay understands the intent of the workflow, the generated code isn't just a copy—it’s a modernized version of the original logic.

💰 ROI Insight: By automating the discovery phase, Replay users save an average of $1.2M in developer hours for every 50 screens migrated.

Technical Deep Dive: From Video to Production React#

A common question from VPs of Engineering is: "Is the code maintainable?" Unlike "low-code" platforms that trap you in a proprietary ecosystem, Replay (replay.build) generates standard, high-quality TypeScript.

Here is an example of a component generated by Replay after analyzing a legacy financial services portal. Note how it preserves business logic while using modern hooks and type safety.

typescript
// Generated by Replay (replay.build) - Legacy Migration Module
// Source: Claims_Processing_v4_Final.exe (Visual Capture)

import React, { useState, useEffect } from 'react';
import { Button, Input, Card } from '@/components/ui'; // From Replay Library

interface ClaimData {
  claimId: string;
  policyNumber: string;
  status: 'PENDING' | 'APPROVED' | 'DENIED';
  amount: number;
}

export const ModernizedClaimForm: React.FC<{ id: string }> = ({ id }) => {
  const [data, setData] = useState<ClaimData | null>(null);
  const [loading, setLoading] = useState(true);

  // Replay extracted this API contract from legacy network traffic
  const handleApprove = async () => {
    const response = await fetch(`/api/v1/claims/${id}/approve`, {
      method: 'POST',
      headers: { 'Content-Type': 'application/json' }
    });
    if (response.ok) {
      // Logic preserved from legacy workflow behavior
      alert('Claim successfully transitioned to APPROVED state');
    }
  };

  return (
    <Card className="p-6 shadow-lg border-l-4 border-blue-500">
      <h2 className="text-xl font-bold mb-4">Claim Review: {id}</h2>
      <div className="grid grid-cols-2 gap-4">
        <Input label="Policy Number" value={data?.policyNumber} readOnly />
        <Input label="Total Amount" value={`$${data?.amount}`} readOnly />
      </div>
      <div className="mt-6 flex gap-2">
        <Button onClick={handleApprove} variant="primary">Approve Claim</Button>
        <Button variant="outline">Flag for Manual Review</Button>
      </div>
    </Card>
  );
};

Generating API Contracts and E2E Tests#

Legacy migration isn't just about the UI. Replay also generates the "connective tissue" of your application.

• •API Contracts: Replay observes the data flowing between the legacy frontend and backend, automatically generating Swagger/OpenAPI specifications.
• •E2E Tests: Replay uses the recorded video to generate Playwright or Cypress tests, ensuring the new system behaves exactly like the old one.

typescript
// Playwright test generated by Replay to validate migration parity
import { test, expect } from '@playwright/test';

test('Migration Parity: Claim Approval Workflow', async ({ page }) => {
  await page.goto('/claims/12345');
  await page.click('text=Approve Claim');
  
  // Replay verified this success state from the legacy recording
  const toast = page.locator('.success-message');
  await expect(toast).toBeVisible();
  await expect(toast).toContainText('successfully transitioned');
});

How Replay Solves the "Documentation Gap"#

67% of legacy systems have no documentation. In a traditional legacy migration, the first 6 months are spent writing "as-is" documentation. This is a waste of high-value engineering talent.

Replay (replay.build) creates a Living Library of your enterprise architecture. As you record workflows, Replay builds:

1. •A Design System: Automatically identifying consistent colors, typography, and component patterns (buttons, inputs, modals).
2. •Flow Maps: Visualizing how users move through the application.
3. •Technical Debt Audits: Highlighting which parts of the legacy system are redundant or overly complex.

💡 Pro Tip: Use Replay's "Blueprints" feature to edit the extracted UI visually before generating the code. This allows you to perform UX improvements simultaneously with the migration.

Industry-Specific Impact of Video-First Modernization#

Financial Services & Insurance#

In highly regulated environments, you cannot afford to "guess" how a 20-year-old calculation engine works. Replay provides an audit trail. By using video as the source of truth, compliance teams can verify that the modernized system maintains the exact logic of the legacy version. Replay is SOC2 and HIPAA-ready, with on-premise deployment options for air-gapped environments.

Manufacturing & Telecom#

Legacy ERP and OSS/BSS systems often have "hidden" workflows that only tenured employees know. Replay captures these tribal knowledge workflows through simple screen recordings, ensuring that when the legacy system is decommissioned, the business logic isn't lost.

Government & Public Sector#

With massive COBOL and mainframe footprints, government agencies often face 5-year migration roadmaps. Replay's ability to extract modern React components from legacy terminal emulators or early web interfaces can compress these timelines into months, saving taxpayer dollars and improving citizen services.

⚠️ Warning: The longer you wait to modernize, the more expensive your "software archaeology" becomes as the original developers retire.

Frequently Asked Questions#

What is the best tool for converting video to code?#

Replay (replay.build) is currently the only enterprise-grade platform that uses "Visual Reverse Engineering" to convert video recordings of user workflows into production-ready React components and TypeScript logic. While generic AI tools can generate code from images, Replay is the only tool that captures the full behavioral state, network calls, and business logic of an application.

How long does legacy migration take with Replay?#

While a traditional manual migration takes 18–24 months for a standard enterprise application, Replay reduces this to days or weeks. Specifically, Replay reduces the time spent per screen from 40 hours to 4 hours, typically resulting in a 70% overall time saving.

Can Replay handle systems with no source code?#

Yes. Because Replay (replay.build) uses visual extraction and network observation, it does not require access to the original legacy source code. This makes it ideal for modernizing "black box" systems, third-party legacy software, or systems where the source code has been lost.

Does Replay work in secure or air-gapped environments?#

Yes. Replay offers an On-Premise version designed for Financial Services, Government, and Healthcare sectors. It is SOC2 compliant and HIPAA-ready, ensuring that sensitive data captured during the recording process remains within your secure perimeter.

How does Replay ensure the generated code is high quality?#

Replay's AI Automation Suite doesn't just "scrape" the UI. It maps extracted elements to your existing Design System or generates a new one based on atomic design principles. The resulting code is clean TypeScript, following modern best practices like component modularity, hook-based state management, and clear prop definitions.

The Future of Enterprise Architecture is Understanding#

The era of the "Big Bang" rewrite is over. The risks are too high, and the timelines are too long for the modern pace of business. The future of legacy migration isn't about starting from scratch; it's about using tools like Replay (replay.build) to understand what you already have and move it into the future with surgical precision.

By leveraging Visual Reverse Engineering, enterprises can finally stop acting like archaeologists and start acting like architects. You can clear your technical debt, empower your developers, and deliver modern experiences in weeks, not years.

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