The $3.6 Trillion Liability: Why Financial Services Must Abandon the "Big Bang" Rewrite

Your legacy core isn't an asset; it's a liability with a $3.6 trillion global price tag. In the financial services sector, this debt isn't just a line item on a balance sheet—it’s the primary reason 70% of modernization initiatives fail to meet their objectives or exceed their timelines. When a Tier-1 bank or a national insurance provider decides to "modernize," the default instinct is the "Big Bang" rewrite. It is a strategy rooted in hubris and destined for disaster.

The reality of financial services architecture is that the "source of truth" isn't the documentation—which is missing or outdated in 67% of systems—and it isn't even the source code, which has been patched, layered, and obfuscated over thirty years. The only true source of truth is the user workflow.

At Replay, we are seeing a fundamental shift in how enterprise architects approach this problem. The future of modernization isn't rewriting from scratch; it’s understanding what you already have through Visual Reverse Engineering.

TL;DR: Financial services firms can reduce modernization timelines by 70% by using Visual Reverse Engineering to extract documented React components and API contracts directly from legacy user workflows, bypassing the "Big Bang" rewrite trap.

The High Cost of "Software Archaeology"#

In most financial services environments—whether it's a mortgage processing system, a claims management portal, or a core banking UI—the technical debt is so dense that developers spend more time on "software archaeology" than on writing new features.

Manual reverse engineering is a grueling process. An average enterprise screen takes approximately 40 hours to document, deconstruct, and recreate in a modern framework like React. For a system with 500 screens, that’s 20,000 man-hours just to reach feature parity. This is why the average enterprise rewrite timeline stretches to 18–24 months, by which point the business requirements have already shifted.

Modernization Methodology Comparison#

⚠️ Warning: Attempting a Big Bang rewrite of a system governing regulated financial data without a 1:1 functional map is the leading cause of "zombie projects"—initiatives that consume budget for years but never reach production.

From Black Box to Documented Codebase#

The primary friction point in financial services modernization is the "Black Box" problem. The original architects are gone. The COBOL or Delphi specialists are retired. The business logic is buried in stored procedures and hard-coded UI validations.

Replay changes the paradigm by using Video as the Source of Truth. By recording a real user performing a high-value workflow—such as onboarding a new wealth management client or processing a complex insurance claim—Replay’s engine captures the state, the data transitions, and the UI structure.

Step 1: Visual Assessment and Recording#

Instead of reading through thousands of lines of legacy Java or .NET, you record the application in action. Replay captures every interaction, mapping the visual elements to their underlying functional requirements.

Step 2: Automated Extraction#

The Replay AI Automation Suite analyzes the recording to generate modern, modular React components. This isn't just a "screen scrape"; it's a deep extraction of the DOM structure, CSS patterns, and state transitions.

Step 3: API Contract Generation#

For financial services, the UI is only half the battle. Replay generates the API contracts and E2E tests required to ensure the new frontend communicates perfectly with the existing (or new) backend services.

Step 4: Technical Debt Audit#

The platform performs an automated audit, identifying which parts of the legacy logic are redundant and which must be preserved in the modern stack.

💰 ROI Insight: By moving from 40 hours per screen to 4 hours with Replay, a mid-sized financial institution can save upwards of $1.2M in labor costs on a 200-screen modernization project.

The Technical Reality: Generated React Components#

When we talk about "generating code," enterprise architects are rightfully skeptical. They expect "spaghetti code" or unmaintainable auto-generated garbage. Replay is different. It generates clean, typed, and modular React components that adhere to your specific Design System.

typescript
// Example: Replay-Generated Component for a Loan Application Summary
// Extracted from a legacy Oracle Forms workflow

import React, { useState, useEffect } from 'react';
import { Button, Card, Grid, Typography } from '@/components/ui'; // Integrated with your Design System
import { useLoanData } from '@/hooks/api/useLoanData';

interface LoanSummaryProps {
  applicationId: string;
  onApprove: (id: string) => void;
}

export const LoanApplicationSummary: React.FC<LoanSummaryProps> = ({ applicationId, onApprove }) => {
  const { data, loading, error } = useLoanData(applicationId);

  // Business logic preserved: Validation for debt-to-income ratio
  const isEligible = data ? (data.monthlyDebt / data.monthlyIncome) < 0.43 : false;

  if (loading) return <Typography>Loading application data...</Typography>;

  return (
    <Card className="p-6 shadow-lg border-l-4 border-blue-600">
      <Grid container spacing={4}>
        <Grid item xs={12}>
          <Typography variant="h4">Application Summary: {data?.clientName}</Typography>
        </Grid>
        <Grid item xs={6}>
          <Typography variant="label">Requested Amount</Typography>
          <Typography variant="value">${data?.requestedAmount.toLocaleString()}</Typography>
        </Grid>
        <Grid item xs={6}>
          <Typography variant="label">Credit Score</Typography>
          <Typography color={data?.creditScore > 700 ? 'green' : 'red'}>
            {data?.creditScore}
          </Typography>
        </Grid>
      </Grid>
      
      <div className="mt-8 flex gap-4">
        <Button 
          variant="primary" 
          disabled={!isEligible}
          onClick={() => onApprove(applicationId)}
        >
          Approve Application
        </Button>
        <Button variant="outline">Flag for Manual Review</Button>
      </div>
    </Card>
  );
};

This isn't just a UI template. Replay identifies the Business Logic Preserved from the legacy system—like the specific debt-to-income ratio threshold (0.43) used in the example above—and ensures it's documented and carried over into the modern implementation.

Security and Compliance in Regulated Environments#

In financial services, "cloud-only" is often a non-starter. Whether it's the SEC, FINRA, or GDPR, the regulatory burden is immense. Replay was built specifically for these constraints:

• •SOC2 & HIPAA Ready: Our data handling processes meet the highest standards of security.
• •On-Premise Availability: For organizations that cannot let their source code or user data leave their network, Replay offers a fully air-gapped on-premise deployment.
• •PII Redaction: Our AI suite automatically identifies and redacts Personally Identifiable Information (PII) during the recording and extraction process, ensuring compliance with privacy regulations.

💡 Pro Tip: When modernizing, use Replay to generate your E2E tests simultaneously. This provides an immediate "Safety Net" that proves the new system behaves exactly like the legacy one—a critical requirement for regulatory audits.

typescript
// Example: Generated Playwright E2E Test for Regression Testing
import { test, expect } from '@playwright/test';

test('verify loan approval workflow parity', async ({ page }) => {
  await page.goto('/loan-summary/APP-88291');
  
  // Replay captured the specific legacy selectors and mapped them to modern IDs
  const approveButton = page.locator('button:has-text("Approve Application")');
  
  // Ensure the business logic extracted (DTI < 0.43) is functioning
  await expect(approveButton).toBeEnabled();
  
  await approveButton.click();
  await expect(page.locator('.success-message')).toContainText('Application Approved');
});

The "Flows" Architecture: Mapping the Enterprise#

Legacy systems are rarely a single application; they are a web of interconnected flows. A single "customer service" portal might touch five different backend systems.

Replay's Flows feature visualizes this architecture. As users record their workflows, Replay maps the journey across different screens and systems, creating a live architectural diagram of how information actually moves through your organization. This eliminates the need for months of stakeholder interviews and "whiteboard archaeology."

Why Financial Services Leaders are Choosing Replay:#

• •Library (Design System): Automatically map legacy UI elements to your modern React design system, ensuring brand consistency across the entire portfolio.
• •Blueprints (Editor): A low-code/no-code environment where architects can tweak the extracted components before they are committed to the codebase.
• •AI Automation Suite: Generates documentation that actually stays up to date because it's linked to the visual state of the application.

Frequently Asked Questions#

How long does legacy extraction take with Replay?#

While a manual rewrite takes 18-24 months, Replay typically reduces this to 2-8 weeks depending on the complexity of the workflows. We focus on "high-value flows" first, allowing for an iterative, low-risk rollout rather than a Big Bang launch.

What about business logic preservation?#

Replay doesn't just look at the UI; it monitors data state changes and network calls. This allows our AI to identify the underlying business rules (e.g., "if credit score < 600, disable the 'Approve' button"). These rules are then surfaced in the documentation and reflected in the generated React code.

Can Replay handle legacy technologies like Mainframe, Delphi, or PowerBuilder?#

Yes. Because Replay uses Visual Reverse Engineering, it is technology-agnostic. If a user can see it on a screen and interact with it, Replay can record it, analyze it, and extract the functional requirements and UI structure into modern React components.

Does this replace my development team?#

No. Replay is a force multiplier for your engineering team. It removes the "grunt work" of manual documentation and UI recreation (the 40 hours per screen), allowing your senior architects to focus on high-level system design, security, and integration.

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