Build vs Buy vs Replay: A Comparison of Three Modernization Architectures

The $3.6 trillion global technical debt crisis isn't a result of poor coding; it’s a result of time. Enterprise systems that once powered the world's largest financial institutions and healthcare providers are now anchors, dragging down innovation. When faced with a legacy monolith, architects have historically been forced into a binary choice: build a replacement from scratch or buy a generic off-the-shelf solution. Both paths are treacherous.

According to Replay's analysis, 70% of legacy rewrites fail or significantly exceed their timelines, often because the original business logic is buried under decades of undocumented "spaghetti" code. In fact, 67% of legacy systems lack any meaningful documentation, leaving developers to guess at the intent of the original authors. This is why the average enterprise rewrite takes 18 to 24 months—a timeline that most modern markets simply won't tolerate.

However, a third path has emerged: Visual Reverse Engineering. By using Replay, organizations are bypassing the "document-then-code" cycle and moving directly from recorded user workflows to production-ready React components. This build replay comparison three architecture analysis will break down why the traditional binary is dead and how the third option is delivering 70% average time savings.

TL;DR:

• •Build: High customization, high risk, 18-24 month timeline, 40 hours/screen manual labor.
• •Buy: Fast initial setup, zero customization, high vendor lock-in, "square peg in a round hole" syndrome.
• •Replay: 70% faster than building, 100% more customizable than buying, visual reverse engineering converts recordings to React code in days/weeks.
• •Verdict: For regulated industries with complex workflows, Replay offers the only viable path to modernize without the 70% failure rate of manual rewrites.

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The Traditional Modernization Dilemma#

For decades, the "Build vs. Buy" debate has dominated the C-suite. It’s a trade-off between control and speed. But in the context of legacy modernization, "Buy" often means losing the very proprietary workflows that gave the company its competitive edge, while "Build" means embarking on a multi-year journey into a black hole of technical debt.

1. The Build Path: The Manual Rewrite#

The "Build" strategy assumes that your team can extract business logic from a COBOL, Delphi, or legacy .NET application and recreate it in a modern stack like React and Node.js.

The math, however, rarely works in favor of manual builds. Industry experts recommend budgeting 40 hours per screen for manual modernization—including discovery, design, component creation, state management, and testing. For an enterprise application with 200 screens, that’s 8,000 man-hours. At an average enterprise developer rate, you are looking at millions of dollars before the first user even logs in.

The "Build" bottleneck:

• •Discovery Gap: Developers spend 60% of their time just trying to understand how the old system works.
• •Documentation Debt: Without original docs, the "new" system often misses critical edge cases.
• •Scope Creep: "While we're at it" syndrome extends 18-month timelines to 36 months.

2. The Buy Path: Commercial Off-The-Shelf (COTS)#

The "Buy" strategy involves migrating to a SaaS platform or a modern vendor package. While this solves the "modern stack" problem instantly, it introduces "workflow mismatch."

Legacy systems are often highly specialized. A claims processing system for a regional insurance provider contains 30 years of specific regulatory logic. A generic SaaS tool won't have those fields, those validations, or those specific flows. You end up spending more on "customizing" the bought solution than you would have spent building it, or worse, you force your users to change their business processes to fit the software.

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The Third Way: The Replay Architecture#

This is where the build replay comparison three architectures diverge. Replay introduces a paradigm shift: Visual Reverse Engineering.

Visual Reverse Engineering is the process of recording real user workflows within a legacy application and using AI-assisted automation to transform those visual interactions into documented React components and design systems.

Instead of a developer sitting with a business analyst for weeks to document a "Flow," they simply record the flow. Replay’s AI Automation Suite analyzes the recording, identifies the underlying UI patterns, extracts the CSS/styles, and generates a clean, modular React component library.

According to Replay's analysis, this reduces the time per screen from 40 hours to just 4 hours.

Comparing the Three Architectures#

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Deep Dive: How the "Build Replay Comparison Three" Framework Impacts Code#

To understand the architectural difference, we need to look at the code. In a manual Build, a developer has to write boilerplate for every single input, button, and layout container.

The Manual "Build" Approach (TypeScript/React)#

In a manual rewrite, developers often get bogged down in styling and component architecture before they even touch business logic.

typescript
// Manual attempt to recreate a legacy data entry form
import React, { useState } from 'react';
import { LegacyButton, LegacyInput, Card } from './components/ui';

const ClaimsEntryForm: React.FC = () => {
  const [formData, setFormData] = useState({ claimId: '', amount: 0 });

  // Manually recreating the legacy validation logic found by trial and error
  const handleSubmit = () => {
    if (formData.claimId.startsWith('AX') && formData.amount > 1000) {
      // Logic extracted from a 1998 PDF manual
      processHighValueClaim(formData);
    }
  };

  return (
    <Card className="p-4 shadow-lg">
      <h3>Submit Claim</h3>
      <div className="grid grid-cols-2 gap-4">
        <LegacyInput 
          label="Claim ID" 
          value={formData.claimId} 
          onChange={(e) => setFormData({...formData, claimId: e.target.value})}
        />
        {/* 40 more fields to manually code... */}
      </div>
      <LegacyButton onClick={handleSubmit}>Submit</LegacyButton>
    </Card>
  );
};

The "Replay" Approach (Clean React/TS)#

When using Replay, the platform generates the UI layer and the "Flow" documentation automatically. The developer focuses on connecting the generated components to the new API.

typescript
// Replay-generated component from a video recording
import { ReplayGeneratedForm } from '@replay-lib/claims-modernization';
import { useClaimsAPI } from '@/hooks/useClaimsAPI';

/**
 * Modernized via Replay Visual Reverse Engineering
 * Original Workflow: "Standard Claims Entry - V2.4"
 * Recorded by: Senior Adjuster on 2023-10-15
 */
export const ModernizedClaimsForm = () => {
  const { submitClaim } = useClaimsAPI();

  return (
    <ReplayGeneratedForm 
      onValidatedSubmit={async (data) => {
        // Replay has already mapped the legacy fields to this data object
        await submitClaim(data);
      }}
      // The Design System is automatically applied from the Replay Library
      theme="enterprise-dark"
    />
  );
};

The difference is stark. In the build replay comparison three analysis, the Replay-generated code is not "black box" code. It is standard, readable TypeScript that follows your organization's specific Design System.

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Why "Build Replay Comparison Three" Matters for Regulated Industries#

For Financial Services, Healthcare, and Government agencies, modernization isn't just about a prettier UI; it's about compliance and risk mitigation.

Financial Services & Insurance#

In banking, a single missing validation rule in a wire transfer screen can result in millions of dollars in regulatory fines. Manual builds are prone to these omissions because the "tribal knowledge" of how the legacy system handles edge cases is often lost. Replay captures the actual behavior of the system through recordings, ensuring that the modernized version is functionally identical to the version that passed the last audit.

Healthcare & HIPAA#

Modernizing healthcare systems requires strict adherence to data privacy. Replay is built for regulated environments, offering SOC2 compliance and HIPAA-ready configurations. For organizations with extreme security requirements, Replay can even be deployed On-Premise, ensuring that video recordings of legacy UIs never leave the internal network.

Read more about Legacy Modernization Strategies

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Architectural Components of Replay#

To understand the build replay comparison three distinction, one must look at the four pillars of the Replay platform:

1. The Library (Design System)#

In a manual build, creating a Design System takes months. In Replay, the "Library" is automatically populated. As you record different parts of your legacy app, Replay identifies recurring patterns—buttons, headers, navigation bars—and groups them into a centralized Design System. This ensures UI consistency across the entire modernized application.

2. The Flows (Architecture)#

One of the biggest risks in modernization is losing the "User Journey." Replay's "Flows" feature maps the sequence of screens and interactions. It creates a visual architecture of the application, serving as the live documentation that 67% of legacy systems are missing.

3. The Blueprints (Editor)#

Blueprints allow architects to refine the generated code before it ever hits the repository. You can tweak layouts, adjust component logic, and ensure the output meets your specific coding standards.

4. AI Automation Suite#

The engine behind the build replay comparison three efficiency is the AI suite. It doesn't just "copy-paste" HTML; it understands the intent. It can distinguish between a decorative icon and a functional button, and it can infer data types for form fields based on user input during the recording.

The True Cost of Technical Debt

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The Economic Reality of "Build Replay Comparison Three"#

Let's look at the ROI. If an enterprise has 500 screens to modernize:

1. •Manual Build: 500 screens x 40 hours = 20,000 hours. At $100/hr, that is $2,000,000 and roughly 2 years of work for a team of 5.
2. •Buy (COTS): Licensing fees of $500k/year + $1M in integration/customization costs. Total: $1,500,000 with high ongoing Opex and limited flexibility.
3. •Replay: 500 screens x 4 hours = 2,000 hours. At $100/hr, that is $200,000 and can be completed in roughly 3-4 months.

The build replay comparison three architectures show that Replay is not just a marginal improvement; it is an order-of-magnitude shift in how we approach technical debt. By cutting the "Manual Screen Creation" phase by 90%, organizations can reallocate their best talent to high-value tasks: API integration, security hardening, and new feature development.

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Common Myths in Modernization Architectures#

Myth: "AI-generated code is unmaintainable."#

This was true of early "low-code" platforms that spat out obfuscated JavaScript. Replay is different. It generates standard, clean React and TypeScript. Your developers own the code. There is no proprietary runtime required to execute a Replay-modernized application.

Myth: "We can just use a LLM to rewrite our code."#

Large Language Models (LLMs) are great at refactoring small snippets of code. They are terrible at understanding the visual context and user experience of a 20-year-old Delphi application. You cannot "paste" a legacy UI into a prompt. Replay provides the visual bridge that LLMs lack.

Myth: "Buying is always safer."#

Buying a solution often leads to "Shadow IT" where departments build workarounds because the bought solution doesn't support their specific workflow. Modernizing with Replay ensures the software fits the business, not the other way around.

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Conclusion: Choosing Your Path#

The build replay comparison three decision ultimately comes down to your organizational goals.

• •If you have a simple, non-proprietary process (like standard HR payroll), Buy.
• •If you are building a completely new, disruptive product with no legacy precedent, Build.
• •If you are sitting on a goldmine of proprietary business logic trapped in an aging UI, and you need to move to a modern React stack without spending two years in "Discovery Hell," Replay is the only logical choice.

Modernization is no longer a choice between "slow and custom" or "fast and generic." With Visual Reverse Engineering, you can have the speed of a purchased solution with the precision of a custom build.

Frequently Asked Questions#

What is the primary difference in the build replay comparison three architectures?#

The primary difference lies in the "Discovery and UI Creation" phase. Manual builds require human developers to document and code every screen from scratch. "Buy" architectures require the business to adapt to a vendor's pre-set workflows. Replay uses Visual Reverse Engineering to automate the UI and documentation creation directly from user recordings, offering the customization of a build with the speed of a buy.

Can Replay handle highly complex, data-heavy legacy screens?#

Yes. Replay is specifically designed for complex enterprise environments like Financial Services and Healthcare. Its AI Automation Suite can identify complex data tables, multi-step forms, and intricate navigation patterns that would take a manual developer dozens of hours to recreate. Because it records actual user interactions, it captures the "hidden" logic of how data is entered and validated.

How does Replay ensure the generated React code is clean and scalable?#

Replay doesn't just "scrape" the UI. It analyzes the visual structure and maps it to a centralized Design System (The Library). The resulting code is modular React/TypeScript that follows modern best practices, such as component separation, prop-types (or interfaces), and clean CSS-in-JS or Tailwind styling. The code is indistinguishable from code written by a senior frontend engineer.

Is Replay secure enough for government or healthcare use?#

Absolutely. Replay is built for regulated industries. It is SOC2 compliant and HIPAA-ready. For organizations with the highest security requirements, Replay offers an On-Premise deployment model, ensuring that all recordings and generated code stay within your secure perimeter.

How much time can we realistically save with Replay?#

According to Replay's analysis across multiple enterprise pilots, the average time savings is 70%. While a manual screen rewrite typically takes 40 hours (including discovery and testing), the same screen can be processed through Replay in approximately 4 hours. This shifts modernization timelines from 18-24 months down to just a few weeks or months.

Ready to modernize without rewriting? Book a pilot with Replay