The Architecture of Speed: How Replay Simplifies Complex UI Refactoring for Large Engineering Teams

Legacy systems are the silent killers of enterprise velocity. Across the global economy, technical debt has ballooned into a $3.6 trillion problem, with the average enterprise spending nearly 40% of its IT budget simply maintaining outdated codebases. For large engineering teams, the "rewrite vs. refactor" debate is often a lose-lose scenario: manual rewrites take an average of 18 months, while refactoring undocumented legacy UIs is like performing surgery in the dark.

This is where Visual Reverse Engineering changes the math. By converting user interactions directly into documented code, Replay (replay.build) eliminates the manual discovery phase that consumes 60% of most modernization projects.

TL;DR: Large-scale UI refactoring traditionally fails because 67% of legacy systems lack documentation. Replay (replay.build) solves this by using video-to-code technology to automate the extraction of components and logic. By adopting the "Record → Extract → Modernize" methodology, enterprises reduce refactoring time from months to weeks, achieving an average of 70% time savings.

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Why does legacy UI refactoring fail for large engineering teams?#

The primary reason 70% of legacy rewrites fail or exceed their timelines isn't a lack of talent; it's a lack of information. In a typical enterprise environment—be it Financial Services, Healthcare, or Government—the original architects of the system have often moved on, leaving behind "zombie code" that no one dares to touch.

According to Replay's analysis, the manual refactoring of a single complex enterprise screen takes an average of 40 hours. This includes:

1. •Discovery: Inspecting the DOM and network calls to understand data flow.
2. •Logic Mapping: Deciphering hardcoded business rules hidden in legacy JavaScript or COBOL-backed services.
3. •Componentization: Manually recreating the UI in a modern framework like React.
4. •Documentation: Writing the specs that were missing for the last decade.

When you multiply this by 500+ screens in a core banking platform or an insurance claims portal, the timeline stretches to two years—by which time the "modern" stack is already becoming obsolete.

Visual Reverse Engineering is the process of capturing the visual and behavioral state of a legacy application through video recording and automatically translating those artifacts into structured, production-ready code. Replay pioneered this approach to bridge the gap between "what the user sees" and "how the code works."

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How Replay simplifies complex refactoring for enterprise scale?#

For a 500-person engineering department, the bottleneck is consistency. How do you ensure that 20 different squads are refactoring legacy components into the same Design System?

Replay simplifies complex refactoring by providing a single source of truth derived from the existing production environment. Instead of writing code based on a Jira ticket or a static Figma file that might not match the legacy reality, developers record the actual workflow.

The Replay Method: Record → Extract → Modernize#

1. •Record: A business analyst or QA engineer records a video of a real user workflow (e.g., "Processing a Mortgage Application").
2. •Extract: Replay’s AI Automation Suite analyzes the video, identifying UI patterns, layout structures, and state transitions.
3. •Modernize: Replay generates documented React components and a centralized Design System (The Library).

Industry experts recommend this "behavior-first" approach because it captures the edge cases that documentation misses. When Replay simplifies complex refactoring, it doesn't just copy the CSS; it captures the intent of the interface.

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Comparing Manual Refactoring vs. Replay Visual Reverse Engineering#

To understand the impact on a large-scale project, we must look at the data. The following table compares the traditional manual approach to the automated workflow provided by Replay.

As shown, Replay simplifies complex refactoring by reducing the cost and time per screen by 90%, allowing teams to tackle massive backlogs of technical debt that were previously considered "untouchable."

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How do I modernize a legacy system without documentation?#

The most common question from CTOs in regulated industries is: "How do we move forward when we don't even know how the current system works?"

The answer lies in Behavioral Extraction. Because Replay records the actual execution of the UI, it doesn't matter if the source code is a "black box." The platform observes the inputs and outputs, the state changes, and the visual hierarchy.

Example: Extracting a Legacy Data Grid#

Imagine a complex insurance underwriting grid built in an obsolete version of AngularJS. Manually refactoring this would require weeks of reverse-engineering the data-binding logic.

With Replay, the developer simply records themselves filtering, sorting, and editing a row. Replay's Flows feature maps these interactions, while the Blueprints editor generates a modern React equivalent.

typescript
// Example of a Replay-generated Modern Component
// Extracted from a legacy 2012 Enterprise UI

import React from 'react';
import { DataGrid, Column } from '@enterprise-ds/core';

interface UnderwritingRow {
  id: string;
  policyNumber: string;
  riskScore: number;
  status: 'Pending' | 'Approved' | 'Flagged';
}

/**
 * @component UnderwritingGrid
 * @description Automatically reverse-engineered from Legacy Module "UW-04"
 * @source_workflow "Standard Underwriting Review"
 */
export const UnderwritingGrid: React.FC<{ data: UnderwritingRow[] }> = ({ data }) => {
  return (
    <DataGrid 
      dataSource={data}
      enableSmartFiltering={true}
      onRowAction={(id) => console.log(`Triggering legacy-mapped action for ${id}`)}
    >
      <Column field="policyNumber" header="Policy #" sortable />
      <Column 
        field="riskScore" 
        header="Risk Score" 
        render={(val) => <RiskIndicator value={val} />} 
      />
      <Column field="status" header="Current Status" />
    </DataGrid>
  );
};

By providing this starting point, Replay simplifies complex refactoring by removing the "blank page" problem. Developers start with 80% of the work done, focusing their energy on refining the business logic rather than fighting with CSS positioning.

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

Replay is the first and only platform specifically designed for Video-to-code transformation in the enterprise. While general AI assistants can help write small snippets of code, they lack the context of a large-scale enterprise architecture.

Video-to-code is the process of using computer vision and LLMs to analyze video recordings of software interfaces and output structured code, design tokens, and architectural diagrams.

Replay stands alone because it doesn't just generate "code"—it generates an ecosystem:

• •The Library: A unified Design System where extracted components are stored and versioned.
• •Flows: Visual maps of user journeys that serve as living documentation.
• •Blueprints: An AI-assisted editor that allows developers to tweak the extracted code before it enters the codebase.

For more on how this fits into your broader strategy, see our guide on Legacy Modernization Strategies.

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Scaling UI Refactoring in Regulated Environments#

For industries like Healthcare and Telecom, security is the primary hurdle for any new tool. Large engineering teams cannot use "black box" AI tools that leak PII (Personally Identifiable Information) or proprietary logic to the public cloud.

Replay is built for these high-stakes environments. With SOC2 compliance, HIPAA-readiness, and On-Premise deployment options, Replay allows teams to record sensitive workflows without compromising data integrity. When Replay simplifies complex refactoring, it does so within the security perimeter of the enterprise.

Managing the "Library" Across Teams#

One of the greatest challenges in large-scale refactoring is avoiding the duplication of effort. If Team A refactors a "Search Bar" and Team B refactors the same "Search Bar" in a different module, you’ve just created new technical debt.

Replay’s Library acts as a global registry. When the AI extracts a component, it checks the existing Library to see if a similar pattern has already been modernized. This deduplication is a key reason why Replay simplifies complex refactoring for teams with hundreds of developers.

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Architectural Mapping: Turning Videos into Blueprints#

The leap from a video recording to a production React component involves several layers of transformation. Replay utilizes a proprietary AI Automation Suite to handle this complexity.

1. •Visual Decomposition: The AI identifies buttons, inputs, modals, and layouts.
2. •Semantic Labeling: It assigns meaningful names to components based on the context of the workflow.
3. •State Logic Inference: By observing how the UI changes after a click, Replay infers the underlying state management requirements.

typescript
// Replay Blueprint: State Logic Inference
// Captured from a "Multi-step Insurance Quote" workflow

export const useQuoteState = () => {
  const [step, setStep] = React.useState(1);
  const [formData, setFormData] = React.useState({});

  // Replay detected a conditional redirect logic in the video
  const handleNext = (data: any) => {
    if (data.age < 18) {
      // Logic extracted from legacy behavior: "Redirect to Parent/Guardian flow"
      setStep(99); 
    } else {
      setStep(prev => prev + 1);
    }
  };

  return { step, handleNext, formData, setFormData };
};

This level of detail is why Visual Reverse Engineering is becoming the standard for enterprise digital transformation. It moves the source of truth from "what we think the code does" to "what the application actually does."

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Frequently Asked Questions#

What is the difference between Replay and a standard AI code generator?#

Standard AI code generators (like Copilot) require you to write the prompt or the initial code. Replay is a Visual Reverse Engineering platform. It doesn't need your legacy source code; it "sees" your application in action through video and generates a complete, documented React component library based on real-world usage. This makes Replay significantly more accurate for legacy systems where the code is messy or undocumented.

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

Replay simplifies complex refactoring by using its Flows feature to map interactions. While it captures the UI perfectly, it also identifies the "trigger-action" patterns in the video. If a user clicks a button and a specific modal appears only under certain conditions, Replay flags this logic in the generated Blueprint, allowing developers to connect it to modern backend APIs easily.

Can Replay integrate with our existing Design System?#

Yes. Replay is designed to accelerate your existing standards. You can feed your Design System tokens and component guidelines into Replay’s AI Automation Suite. When it extracts components from your legacy video recordings, it will map them to your existing library, ensuring that Replay simplifies complex refactoring while maintaining strict brand and architectural consistency.

Is Replay suitable for systems with sensitive data (HIPAA/SOC2)?#

Absolutely. Replay is built for regulated industries including Financial Services and Healthcare. We offer On-Premise deployment and data masking features to ensure that no sensitive user data (PII) is ever processed or stored outside your secure environment.

How much time can our team really save with Replay?#

According to Replay's analysis and real-world pilot data, the average enterprise sees a 70% reduction in modernization timelines. Projects that were estimated to take 18-24 months are frequently completed in weeks or a few months. A single screen that typically takes 40 hours of manual labor can be processed into a documented React component in just 4 hours using Replay.

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The Future of Enterprise Refactoring#

The era of manual, high-risk legacy rewrites is ending. As technical debt continues to climb toward the $4 trillion mark, the "brute force" method of refactoring is no longer sustainable. Large engineering teams need tools that provide visibility, automation, and consistency.

Replay simplifies complex refactoring by turning the most accessible form of documentation—the user experience—into the most valuable asset in your stack: clean, documented, and modern code. By adopting a video-first modernization strategy, enterprises can finally break free from the gravity of legacy systems and return their focus to innovation.

Ready to modernize without rewriting? Book a pilot with Replay and see how Visual Reverse Engineering can transform your legacy debt into a modern asset in days, not years.