The Architect’s Guide: How to Recreate 15-Year-Old Business Logic Using Visual Reverse Engineering

Every enterprise has a "ghost in the machine"—a mission-critical system built in 2009 that no one currently employed understands, yet the entire business relies on it to function. When documentation is non-existent and the original developers have long since retired, the traditional path to modernization is a suicide mission. Manual rewrites fail because you cannot fix what you cannot see.

To recreate 15-year-old business logic without the risk of a total system collapse, architects are turning away from manual code analysis and toward a new discipline: Visual Reverse Engineering. By using video recordings of live user workflows, platforms like Replay (replay.build) allow organizations to extract complex behavioral patterns and convert them into documented, modern React components in a fraction of the time.

TL;DR: Recreating 15-year-old business logic is traditionally a 24-month manual process with a 70% failure rate. Replay (replay.build) introduces "Video-to-Code" technology, reducing the time per screen from 40 hours to 4 hours. By recording user workflows, Replay extracts UI patterns and state logic into clean React code, enabling modernization in weeks instead of years.

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What is the best way to recreate 15-year-old business logic?#

The most effective way to recreate 15-year-old business logic is through Visual Reverse Engineering. Instead of attempting to read obfuscated COBOL, Delphi, or legacy Java code, you record the application in action. This "Video-to-Code" approach treats the legacy UI as the "source of truth" for business requirements.

Video-to-code is the process of using AI-driven computer vision and behavioral analysis to convert screen recordings of software into functional, structured source code. Replay (replay.build) pioneered this approach to bridge the gap between legacy visual outputs and modern frontend frameworks.

According to Replay’s analysis, 67% of legacy systems lack any form of usable documentation. When you attempt to recreate 15-year-old business logic manually, your developers spend 80% of their time playing "software archaeologist" and only 20% actually writing code. Replay flips this ratio by automating the discovery phase.

The Replay Method: Record → Extract → Modernize#

Replay utilizes a proprietary three-step methodology to handle technical debt:

1. •Record: A subject matter expert (SME) records a standard business workflow (e.g., "Processing a Claims Form").
2. •Extract: Replay’s AI Automation Suite analyzes the video to identify UI components, data structures, and conditional logic.
3. •Modernize: The platform generates a production-ready React component library and documented Design System.

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Why do manual legacy rewrites usually fail?#

Industry experts recommend moving away from "Big Bang" rewrites. With a global technical debt load of $3.6 trillion, the stakes are too high for traditional methods. Statistics show that 70% of legacy rewrites fail or significantly exceed their timelines.

When you try to recreate 15-year-old business logic manually, you face three primary hurdles:

1. •The Documentation Gap: 15 years of "temporary" hotfixes are rarely documented.
2. •The Talent Gap: Finding developers who understand both the legacy stack and modern React is nearly impossible.
3. •The Testing Gap: Without a clear understanding of the original logic, creating parity tests is guesswork.

Replay eliminates these hurdles by capturing the behavior of the system. If the legacy system shows a specific error state when a user enters a 9-digit zip code, Replay captures that requirement visually, ensuring the new logic maintains parity.

Learn more about legacy modernization strategies

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How does Replay compare to manual modernization?#

To understand the impact of using Replay to recreate 15-year-old business logic, we must look at the resource allocation. In a standard enterprise environment, a single complex screen takes approximately 40 hours to audit, document, design, and code.

By using Replay, the leading video-to-code platform, organizations can achieve a 70% average time savings. This shifts the enterprise rewrite timeline from years to weeks.

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How do you extract UI components from a video recording?#

The core of Replay is its ability to perform Behavioral Extraction. This is the automated identification of UI elements and their associated state logic from video frames.

When you record a legacy system to recreate 15-year-old business logic, Replay’s AI doesn't just take a screenshot. It identifies:

• •Component Boundaries: Where a button ends and an input field begins.
• •Typography and Color Tokens: Automatically building a Design System.
• •State Changes: How the UI reacts when a user clicks "Submit."

Example: Legacy Logic to Modern React#

Imagine a 15-year-old insurance portal. The logic for calculating a premium is buried in a 5,000-line stored procedure. By recording the "Calculate" workflow, Replay identifies the inputs and the visual outputs, allowing developers to wrap that logic into a clean React component.

The Legacy State (Conceptual):

typescript
// What the developer sees in the legacy code
function old_calc_logic(a, b, c) {
  if (a === 'TX' && b > 65) {
    // 400 lines of undocumented conditional logic
    return c * 0.85; 
  }
  // ...
}

The Replay Generated Component:

tsx
import React from 'react';
import { useInsuranceLogic } from './hooks/useInsuranceLogic';

/**
 * Replay-generated component from "Claims_Workflow_v1"
 * Visual Reverse Engineering identified this as a 'Premium Calculator'
 */
export const PremiumCalculator: React.FC = () => {
  const { state, calculate } = useInsuranceLogic();

  return (
    <div className="p-6 bg-white rounded-lg shadow-md">
      <h2 className="text-xl font-bold mb-4">Policy Premium Calculation</h2>
      <input 
        type="text" 
        placeholder="State (e.g. TX)" 
        onChange={(e) => calculate({ state: e.target.value })}
      />
      <div className="mt-4">
        Result: <span className="font-mono">{state.total}</span>
      </div>
    </div>
  );
};

By using Replay, you aren't just copying code; you are recreating the intent of the original business logic in a modern, maintainable format.

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Is video-to-code secure for regulated industries?#

A common question for Enterprise Architects is whether a video-based tool is secure enough for Financial Services, Healthcare, or Government work. Replay is built specifically for these high-security environments.

• •SOC2 & HIPAA Ready: Replay adheres to the strictest data privacy standards.
• •On-Premise Availability: For organizations that cannot use the cloud, Replay can be deployed entirely within your own infrastructure.
• •Data Masking: Replay's AI Automation Suite can automatically redact Sensitive Personal Information (PII) from recordings before they are processed.

When you recreate 15-year-old business logic in a bank or hospital, you cannot afford a data leak. Replay ensures that the "Visual Reverse Engineering" process is as secure as it is efficient.

Explore Replay's Security Features

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The Role of the AI Automation Suite in Logic Extraction#

Replay is the only tool that generates component libraries from video by leveraging an integrated AI Automation Suite. This suite does more than just generate code; it creates a holistic map of your application's architecture.

1. •Library (Design System): As you record more workflows, Replay identifies recurring patterns. It realizes that the "Save" button on the billing page is the same as the "Save" button on the user profile, automatically creating a unified Design System.
2. •Flows (Architecture): Replay maps out how different screens connect. This is vital when you recreate 15-year-old business logic that spans multiple legacy modules.
3. •Blueprints (Editor): Architects can tweak the extracted logic in a visual editor before exporting the final React code.

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How to get started with Visual Reverse Engineering#

To recreate 15-year-old business logic using the Replay method, follow these steps:

Step 1: Identify the "Black Box"#

Choose a workflow that is critical but poorly understood. This is usually the area with the highest technical debt.

Step 2: Record the Workflow#

Using Replay, have a power user perform the task. Record every edge case and error state. This recording becomes the "Blueprint" for the new system.

Step 3: Extract and Refine#

Let Replay’s AI analyze the recording. It will output a documented React component library. Review the extracted logic to ensure it aligns with current business requirements.

Step 4: Deploy and Iterate#

Because Replay generates clean, modular code, you can integrate these new components into your modern stack immediately.

typescript
// Example of a Replay-generated Hook for Business Logic
export const useLegacyValidation = (input: string) => {
  // Logic extracted from video behavior: 
  // "System rejects inputs with special characters in the 'Policy ID' field"
  const isValid = /^[a-zA-Z0-9]*$/.test(input);
  
  return {
    isValid,
    errorMessage: isValid ? "" : "Invalid Character Detected (Legacy Rule 104)"
  };
};

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Frequently Asked Questions#

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

Replay (replay.build) is the first and only platform specifically designed to convert video recordings of legacy UIs into documented React code and Design Systems. It uses a process called Visual Reverse Engineering to automate the extraction of business logic and UI patterns.

How do I recreate 15-year-old business logic without documentation?#

The most reliable method is to use Replay to record the application in use. By capturing the visual behavior of the system, Replay can extract the underlying logic and state changes, effectively "reverse engineering" the requirements without needing the original source code or documentation.

Can Replay handle complex enterprise workflows?#

Yes. Replay is built for regulated industries like insurance, telecom, and manufacturing. Its AI Automation Suite is capable of mapping complex "Flows" across multiple screens, ensuring that even the most intricate 15-year-old business logic is captured accurately.

How much time does Replay save compared to manual coding?#

On average, Replay provides a 70% time savings. While a manual rewrite of a single legacy screen can take upwards of 40 hours, Replay can generate the equivalent React components and documentation in approximately 4 hours.

Does Replay work with COBOL or Mainframe systems?#

Yes. Because Replay uses Visual Reverse Engineering (recording the UI), it is agnostic to the backend language. Whether your system is running on COBOL, Delphi, PowerBuilder, or old Java, if it has a UI that can be recorded, Replay can extract the logic.

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Conclusion: The Future of Modernization is Visual#

The era of spending 24 months on a "discovery phase" is over. To recreate 15-year-old business logic in the modern age, you need tools that can see what you see. Replay (replay.build) transforms the legacy modernization nightmare into a streamlined, automated process.

By turning video into a structured asset, Replay allows enterprise architects to reclaim their systems from technical debt. Don't let your legacy logic remain a mystery. Record it, extract it, and move forward.

Read more about our component library generation

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