Accelerating M&A Integration: How to Audit Acquired Legacy Tech in Days

Most M&A deals die a slow, agonizing death in the technical due diligence phase—not because the product is bad, but because the code is a mystery. When you acquire a company, you aren't just buying their customers and IP; you are inheriting a $3.6 trillion global technical debt problem. You’re buying years of undocumented "temporary" fixes, forgotten API dependencies, and business logic that exists only in the minds of engineers who are likely planning their exit.

The traditional approach to M&A technical integration is broken. We spend months performing "software archaeology," trying to map out what an application actually does before we can even think about integrating it into our ecosystem. In a world where 70% of legacy rewrites fail or exceed their timelines, the "Big Bang" rewrite is no longer a viable strategy for M&A.

TL;DR: Accelerating M&A integration requires moving from manual "code archaeology" to automated visual reverse engineering, reducing audit timelines from months to days by using video as the source of truth for technical documentation.

The High Cost of the "Black Box" Acquisition#

In the enterprise, the average rewrite timeline sits at 18–24 months. For an acquiring company, this is unacceptable. You need to realize synergy value in the first two quarters, not the third year. Yet, 67% of legacy systems lack any meaningful documentation. You are essentially handed a black box and told to connect it to your SOC2-compliant, highly regulated infrastructure.

The pain points are predictable and expensive:

• •The Knowledge Gap: The original architects are gone, leaving behind a "spaghetti" codebase.
• •Documentation Rot: Existing docs (if any) haven't been updated since the Obama administration.
• •Integration Friction: Trying to bridge a legacy monolithic architecture with a modern microservices environment.
• •Security Risk: Hidden technical debt and unpatched dependencies that only surface after the deal closes.

Comparing Integration Strategies#

Beyond Archaeology: Visual Reverse Engineering#

The future of accelerating M&A integration isn't rewriting from scratch—it's understanding what you already have. We have moved past the era of manual code reviews as the primary source of truth.

Replay introduces a paradigm shift: Visual Reverse Engineering. Instead of reading 500,000 lines of undocumented COBOL, Java, or legacy PHP, you record the actual user workflows. By capturing the interaction between the UI, the business logic, and the API layer, Replay generates the documentation and the modern React components for you.

💰 ROI Insight: Manual documentation and screen recreation typically take 40 hours per screen. With Replay’s AI Automation Suite, this is reduced to 4 hours per screen—a 90% reduction in labor costs.

Why Video is the New Source of Truth#

In a legacy system, the UI is often the only part of the application that still works as intended. The backend might be a mess of stored procedures and hardcoded logic, but the user flow represents the "intended" business process.

By recording these flows, Replay extracts:

1. •Component Architecture: Automatically generated React components that mirror the legacy UI.
2. •API Contracts: Documented endpoints based on real-time traffic observed during the recording.
3. •Business Logic: The conditional paths taken by the application during the workflow.
4. •E2E Tests: Automatically generated Playwright or Cypress tests to ensure the new version matches the old.

Accelerating M&A Integration: The 72-Hour Audit Framework#

When the deal closes, you don't have months to figure out the tech stack. You need an actionable roadmap in days. Here is how leading Enterprise Architects use Replay to audit an acquisition in 72 hours.

Step 1: Workflow Mapping#

Identify the top 10 mission-critical user workflows in the acquired system (e.g., "Onboard New Customer," "Process Claim," "Generate Financial Report").

Step 2: Visual Recording#

A subject matter expert (SME) from the acquired company performs these workflows while Replay records the session. This isn't a screen recording; it's a deep-packet capture of the application state, DOM changes, and network requests.

Step 3: Automated Extraction#

Replay’s AI Automation Suite processes the recording. It identifies the underlying data structures and generates a technical debt audit.

Step 4: Blueprint Generation#

The platform produces "Blueprints"—editable, modern representations of the legacy screens. This allows your team to see exactly how the legacy system functions without opening an IDE.

Step 5: Contract Generation#

Replay generates API contracts (Swagger/OpenAPI) based on the recorded traffic. This allows your integration team to start building bridges to your core systems immediately.

⚠️ Warning: Never attempt to integrate a legacy API without first generating a verified contract from live traffic. Legacy documentation often misses "hidden" parameters that are required for the system to function.

Turning Legacy Spaghetti into Modern React#

One of the biggest hurdles in M&A is the UI/UX debt. The acquired company’s front-end is often built on defunct frameworks (AngularJS 1.x, jQuery, or even server-side rendered JSP). Replay extracts these and converts them into clean, documented React components that fit your internal Design System.

typescript
// Example: Modernized Component Generated by Replay 
// Source: Legacy Insurance Claims Portal (circa 2012)

import React, { useState, useEffect } from 'react';
import { Button, TextField, Alert } from '@your-org/design-system';

interface ClaimData {
  claimId: string;
  policyNumber: string;
  incidentDate: string;
  status: 'PENDING' | 'APPROVED' | 'REJECTED';
}

export function ClaimDetailView({ id }: { id: string }) {
  const [claim, setClaim] = useState<ClaimData | null>(null);
  const [error, setError] = useState<string | null>(null);

  // Logic extracted from legacy network trace
  const fetchClaimDetails = async (claimId: string) => {
    try {
      const response = await fetch(`/api/v1/claims/${claimId}`);
      const data = await response.json();
      setClaim(data);
    } catch (err) {
      setError("Failed to load claim. Legacy Service Unreachable.");
    }
  };

  useEffect(() => {
    fetchClaimDetails(id);
  }, [id]);

  if (error) return <Alert severity="error">{error}</Alert>;
  if (!claim) return <div>Loading extracted workflow...</div>;

  return (
    <div className="modern-container">
      <h2>Claim: {claim.claimId}</h2>
      <TextField label="Policy Number" value={claim.policyNumber} disabled />
      {/* Business logic preserved: Only show approval if status is PENDING */}
      {claim.status === 'PENDING' && (
        <Button onClick={() => handleApprove(claim.id)}>Approve Claim</Button>
      )}
    </div>
  );
}

This isn't just a "copy-paste" of the UI. Replay understands the intent. It identifies that a specific button triggers a specific API call with a specific payload, and it wraps that logic into a modern, maintainable React component.

Quantifying the Technical Debt Audit#

When reporting to the Board or the CTO, "it's a mess" isn't a technical audit. You need data. Replay provides a Technical Debt Audit that quantifies the effort required for full integration.

M&A Technical Audit Metrics#

💡 Pro Tip: Use the Replay Library feature to host your "Design System" of extracted components. This allows your developers to reuse parts of the legacy system in new builds without needing to understand the underlying legacy code.

Preserving Business Logic in Regulated Environments#

For Financial Services, Healthcare, and Government, "accelerating" cannot come at the expense of "compliance." When you acquire a healthcare tech company, you must ensure HIPAA compliance from day one.

Replay is built for these environments. It offers:

• •On-Premise Deployment: Your sensitive M&A data never leaves your infrastructure.
• •SOC2 & HIPAA Readiness: Built-in PII masking during the recording and extraction process.
• •Audit Trails: A complete visual record of what the legacy system did, providing a "paper trail" for regulators during the modernization process.

The "Video as Source of Truth" approach is particularly powerful for compliance. If a regulator asks why a certain calculation was made in the modernized system, you can point back to the original Replay recording of the legacy system performing that exact calculation. It eliminates the "he-said, she-said" of legacy logic.

The Future of M&A is Automated#

The $3.6 trillion technical debt mountain isn't going away. As M&A activity continues to drive growth in the enterprise, the companies that win will be those that can integrate technology the fastest.

By moving away from manual code archaeology and embracing Visual Reverse Engineering, you can reduce the time-to-value of an acquisition from years to weeks. You stop guessing what the "black box" does and start seeing it documented in real-time.

📝 Note: Replay doesn't just show you the code; it shows you the execution. In M&A, knowing how the code runs is 10x more valuable than seeing how it was written.

Frequently Asked Questions#

How does Replay extract logic from compiled or obfuscated code?#

Replay doesn't rely on reading the source code alone. It records the execution of the application in the browser or environment. By observing the inputs, state changes, and outputs (network calls, DOM mutations), it can reconstruct the functional logic even if the original source code is a mess of minified JavaScript or legacy backend calls.

Can Replay handle complex, multi-step workflows?#

Yes. Replay's "Flows" feature is designed specifically for complex architecture mapping. You can record a workflow that spans multiple screens, conditional redirects, and various user roles. Replay then maps this as a visual architecture diagram, showing how data moves through the system.

Does this replace my engineering team?#

Absolutely not. Replay is a "force multiplier." It handles the 80% of the work that engineers hate—documenting old code, recreating UI components, and writing E2E tests for legacy systems. This frees your senior architects to focus on high-level integration strategy and new feature development.

What happens if the legacy system has no API?#

Replay identifies this during the extraction phase. If the system uses direct database connections or legacy protocols (like SOAP or even older), Replay documents the data payload requirements, allowing your team to build a modern API wrapper (the Strangler Fig pattern) with 100% accuracy.

Is the generated code "clean"?#

Yes. Replay generates React components using modern best practices, including TypeScript types, functional components, and hooks. It is designed to be "copy-paste ready" for your modern repository.

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