The 14-Day Proof of Concept: Validating Your Modernization Strategy Without the Risk

The "Big Bang" rewrite is a $3.6 trillion lie. Every year, enterprise leadership falls for the same trap: the belief that a complete ground-up rebuild will solve technical debt faster than incremental modernization. The reality? 70% of legacy rewrites fail, exceed their timelines, or are abandoned before they ever reach production.

When you are dealing with a black-box system—where the original architects have retired and the documentation is non-existent (a reality for 67% of legacy systems)—guessing is not a strategy. You need a way to validate your modernization path in days, not months. This is where "The 14-Day Proof" changes the economics of the enterprise architecture.

TL;DR: The 14-Day Proof uses visual reverse engineering to extract production-ready React components and API contracts from legacy systems, reducing the validation phase from months to two weeks.

The Archaeology Tax: Why Traditional POCs Fail#

Most modernization Proof of Concepts (POCs) fail because they start with "Software Archaeology." Teams spend 3-6 months just trying to map out dependencies, understand undocumented business logic, and figure out what the legacy UI is actually doing.

The industry average for manually recreating a single complex enterprise screen—including state management, validation logic, and API integration—is roughly 40 hours. In a system with 500+ screens, the math simply doesn't work. You are looking at an 18-24 month timeline before the first user even sees a beta.

The Modernization Landscape#

💰 ROI Insight: By moving from manual recreation (40 hours/screen) to visual extraction with Replay (4 hours/screen), enterprises realize a 90% reduction in front-end development costs during the initial migration phase.

The 14-Day Proof: A Technical Framework#

The goal of a 14-day POC isn't to migrate the entire system; it's to prove that the most complex, high-risk workflows can be extracted, documented, and run in a modern stack (React/TypeScript) without losing business logic.

Phase 1: Workflow Recording (Days 1-3)#

Instead of reading 10-year-old COBOL or minified JavaScript, we use "Video as the Source of Truth." A subject matter expert (SME) performs a standard business process—like processing an insurance claim or a trade settlement—while Replay records the underlying network calls, state changes, and DOM mutations.

Phase 2: Component Extraction (Days 4-7)#

Replay’s AI Automation Suite parses the recording to generate clean, modular React components. This isn't a "screen scrape." It's a structural extraction that identifies:

• •Input validation patterns
• •Hidden state transitions
• •CSS/Styling tokens for the new Design System (Library)
• •API interaction patterns

typescript
// Example: Replay-Generated Component Extract
// Source: Legacy Insurance Portal (v.2012)
// Target: Modern React + Tailwind

import React, { useState, useEffect } from 'react';
import { useClaimsData } from '@/hooks/useClaims';
import { Button, Input, Alert } from '@/components/ui';

export const ClaimsProcessor: React.FC<{ claimId: string }> = ({ claimId }) => {
  const { data, loading, error } = useClaimsData(claimId);
  const [status, setStatus] = useState(data?.status || 'PENDING');

  // Business logic preserved: Legacy 'Rule 402' for auto-adjudication
  const handleAdjudicate = async () => {
    if (data.totalValue < 5000 && data.riskScore < 3) {
      await updateClaimStatus(claimId, 'AUTO_APPROVED');
    } else {
      setStatus('MANUAL_REVIEW_REQUIRED');
    }
  };

  if (loading) return <SkeletonLoader />;

  return (
    <div className="p-6 bg-white rounded-lg shadow-sm">
      <h2 className="text-xl font-bold">{data.policyNumber}</h2>
      <Input 
        value={data.claimAmount} 
        readOnly 
        label="Extracted Claim Amount" 
      />
      <Button onClick={handleAdjudicate}>
        Process via Legacy Logic
      </Button>
    </div>
  );
};

Phase 3: API Contract & Test Generation (Days 8-11)#

A modernization project is only as good as its integration layer. During the 14-day proof, Replay generates OpenAPI (Swagger) specifications based on the actual traffic recorded. This eliminates the "Black Box" problem of the backend.

⚠️ Warning: Never trust legacy documentation. In 85% of our audits, the actual API behavior differed significantly from the existing documentation.

Phase 4: Validation & Handoff (Days 12-14)#

The final stage of the POC is the "Technical Debt Audit." We compare the generated code against the legacy system to ensure 1:1 parity in business logic.

Breaking the "Document or Build" Paradox#

Enterprise Architects often feel forced to choose between documenting the current system (which adds no immediate value) or building the new one (which is risky without documentation).

Replay removes this friction. By recording the workflow, you get the documentation as a byproduct of the build process.

• •Blueprints (Editor): Visualizes the application flow, showing how data moves from Screen A to Screen B.
• •Flows (Architecture): Maps the relationship between the UI and the microservices, identifying redundant API calls.
• •E2E Tests: Automatically generates Playwright or Cypress tests based on the recorded user journey.

yaml
# Generated API Contract from Replay Extraction
openapi: 3.0.0
info:
  title: Legacy Claims API (Extracted)
  version: 1.0.0
paths:
  /api/v1/claims/{id}:
    get:
      summary: Retrieves claim details observed during recording
      parameters:
        - name: id
          in: path
          required: true
          schema:
            type: string
      responses:
        '200':
          description: OK
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Claim'

Solving for Regulated Environments#

For Financial Services and Healthcare, "moving fast" is often synonymous with "violating compliance." The 14-Day Proof must be conducted within the perimeter. Replay is built for these constraints:

• •SOC2 Type II & HIPAA Ready: Data privacy is baked into the extraction.
• •On-Premise Deployment: Keep your source code and recordings within your own VPC.
• •PII Masking: Automatically redact sensitive user data during the recording phase so it never hits the LLM or the extraction engine.

📝 Note: In highly regulated sectors, the "Technical Debt Audit" generated by Replay serves as a critical artifact for compliance officers to prove that the new system maintains the required logic safeguards of the old one.

The 14-Day Proof Checklist#

If you are evaluating a modernization partner or tool, ensure your POC covers these five pillars:

1. •Logic Preservation: Can the tool identify "invisible" business rules hidden in the UI logic?
2. •Code Quality: Is the output "spaghetti" or clean, typed React/TypeScript?
3. •Speed to Hello World: Can you see a functional version of your most complex screen in under 48 hours?
4. •Testability: Does it generate the unit and E2E tests required to maintain the system?
5. •Architectural Insight: Does it provide a map of your technical debt, or just a new coat of paint?

Frequently Asked Questions#

How long does legacy extraction take with Replay?#

While a full enterprise migration depends on the scale, the initial extraction of a complex workflow takes 2-4 days. We typically see a 70% average time savings compared to manual rewrites, moving projects from an 18-month roadmap to a matter of weeks.

What about business logic preservation?#

This is the core of Visual Reverse Engineering. By capturing the state changes and network responses in real-time as a user interacts with the system, Replay identifies the "if/then" logic that often exists only in the client-side code. This logic is then refactored into modern React hooks or service layers.

Does this work with mainframe-backed web apps?#

Yes. As long as there is a web-based front end (even if it's a 20-year-old JSP or ASP.NET app), Replay can record the interactions and extract the modern equivalent. We specialize in "unwrapping" the mainframe by documenting the API calls the web layer makes to those legacy backends.

Is the code maintainable?#

Unlike "no-code" platforms that lock you in, Replay generates standard React, TypeScript, and CSS. Once the code is extracted, it belongs to you. It's indistinguishable from code written by a senior front-end engineer, following your specific design system and linting rules.

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