The Enterprise Architect’s Guide to Video-Based System Documentation

Your legacy system is a black box, and your most senior developer just put in their two-week notice. This is the nightmare scenario for every Enterprise Architect overseeing a $3.6 trillion global technical debt mountain. When 67% of legacy systems lack any meaningful documentation, modernization isn't a coding challenge—it’s an archaeology project.

The traditional "Big Bang" rewrite is a documented failure, with 70% of projects exceeding their timelines or failing entirely. We have spent decades trying to document systems by reading brittle, undocumented COBOL, Java, or Delphi code. It is time to shift the source of truth from the codebase to the user's workflow.

TL;DR: Video-based visual reverse engineering reduces documentation and component extraction time by 70%, transforming legacy "black boxes" into modern React codebases in days rather than years.

The Cost of Manual Archaeology#

The average enterprise rewrite timeline spans 18 to 24 months. Most of that time isn't spent writing new code; it's spent trying to figure out what the old code actually does. We call this "code archaeology."

When you manually document a single legacy screen, the process typically looks like this:

1. •Discovery: Interviewing users who have used the system for 20 years.
2. •Analysis: Digging through thousands of lines of spaghetti code to find the hidden business logic.
3. •Specification: Writing a 50-page PRD that is obsolete by the time it’s finished.
4. •Implementation: Guessing at the API contracts and state transitions.

This manual process takes an average of 40 hours per screen. For a standard enterprise application with 200 screens, you are looking at 8,000 man-hours just to understand the baseline.

💰 ROI Insight: By using Replay, enterprises reduce the time spent per screen from 40 hours to just 4 hours. On a 200-screen project, this saves approximately 7,200 hours of senior engineering time.

A New Framework: Video as the Source of Truth#

Visual Reverse Engineering flips the script. Instead of reading the code to understand the behavior, we record the behavior to generate the code. By capturing real user workflows, we create a high-fidelity record of every state transition, API call, and UI component.

Comparison of Modernization Approaches#

How Visual Reverse Engineering Works#

Replay doesn't just "record a video." It captures the underlying metadata of the application's execution. It maps the visual elements to the business logic, allowing for the automated generation of modern React components and API contracts.

Step 1: Workflow Recording#

The process begins by recording a subject matter expert (SME) performing a standard business process (e.g., "Onboarding a New Insurance Claimant"). As the user interacts with the legacy UI, Replay captures the DOM state, the network requests, and the visual layout.

Step 2: Component Extraction#

The platform analyzes the recording and identifies reusable patterns. It breaks down the monolithic legacy screen into a structured Design System.

typescript
// Example: Generated React component from a Replay video extraction
// This component preserves the business logic captured during the recording
import React, { useState, useEffect } from 'react';
import { LegacyService } from './services/legacy-bridge';

export const ClaimsFormMigrated: React.FC<{ claimId: string }> = ({ claimId }) => {
  const [data, setData] = useState<ClaimData | null>(null);
  const [loading, setLoading] = useState(true);

  // Logic extracted from observed legacy behavior
  useEffect(() => {
    async function loadData() {
      const result = await LegacyService.fetchClaim(claimId);
      // Replay identified that 'Status' field triggers a specific validation
      if (result.status === 'PENDING') {
        result.requiresManualReview = true;
      }
      setData(result);
      setLoading(false);
    }
    loadData();
  }, [claimId]);

  if (loading) return <Spinner />;

  return (
    <div className="modern-layout">
      <header>Claim ID: {data?.id}</header>
      <ValidationWrapper isRequired={data?.requiresManualReview}>
        <Input value={data?.description} onChange={...} />
      </ValidationWrapper>
    </div>
  );
};

Step 3: API Contract Generation#

One of the biggest hurdles in modernization is the "Black Box" API. Often, the original developers are gone, and the documentation is non-existent. Replay monitors the network traffic during the recording to generate precise OpenAPI/Swagger specifications.

yaml
# Generated API Contract from Replay Flow Extraction
openapi: 3.0.0
info:
  title: Legacy Claims API
  version: 1.0.0
paths:
  /v1/claims/{id}:
    get:
      summary: Extracted from 'Process Claim' workflow
      parameters:
        - name: id
          in: path
          required: true
          schema:
            type: string
      responses:
        '200':
          description: Successful extraction
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Claim'

⚠️ Warning: Never attempt a rewrite without first validating your API contracts. 40% of rewrite failures occur because the new frontend cannot properly communicate with the legacy backend.

The Architect’s Toolkit: Library, Flows, and Blueprints#

To manage this at scale, Replay provides three core modules designed for the Enterprise Architect:

1. The Library (Design System)#

As you record different parts of the system, Replay identifies redundant UI elements. It automatically builds a React-based Design System. This prevents the "snowflake" problem where every page has a slightly different version of a button or input field.

2. Flows (Architecture Mapping)#

Flows provide a bird's-eye view of your system's state machine. By stitching together multiple recordings, you can see how data moves from the "Customer Portal" to the "Admin Dashboard" to the "Database." This is documentation that lives and breathes.

3. Blueprints (The Editor)#

Blueprints allow architects to refine the extracted code before it hits the repository. You can swap out legacy API endpoints for modern GraphQL resolvers or adjust the styling to meet new brand guidelines while keeping the core business logic intact.

💡 Pro Tip: Use Flows to identify "Ghost Workflows"—processes that users perform which aren't officially documented but are critical to the business.

Solving the Security and Compliance Hurdle#

In regulated industries like Financial Services, Healthcare, and Government, "sending data to the cloud" is often a non-starter. Modernization tools must respect the data gravity and security requirements of the enterprise.

• •SOC2 & HIPAA Ready: Replay is built with the highest data protection standards.
• •On-Premise Deployment: For air-gapped environments or highly sensitive data, Replay can be deployed entirely within your VPC.
• •PII Masking: During the recording process, sensitive data can be automatically redacted before it ever leaves the local environment.

Case Study: From 18 Months to 6 Weeks#

A major insurance provider was struggling to modernize a 15-year-old claims processing system built in Silverlight. The original estimate for a manual rewrite was 18 months and $2.2 million.

By implementing Replay, they:

1. •Recorded 45 core workflows over 2 weeks.
2. •Automatically generated 80% of the React frontend components.
3. •Identified 12 critical "hidden" business rules that would have been missed in a manual rewrite.
4. •Delivered the modernized MVP in 6 weeks.

📝 Note: The goal isn't just to move faster; it's to move with higher fidelity. Automated extraction eliminates the "human error" inherent in manual documentation.

The Roadmap to Rapid Modernization#

Step 1: Inventory and Prioritization#

Identify the high-value, high-risk screens in your legacy monolith. Don't try to boil the ocean. Start with the screens that have the highest user traffic or the most frequent bug reports.

Step 2: SME Recording Sessions#

Schedule 30-minute sessions with your power users. Have them perform their daily tasks while Replay records in the background. This captures the "unwritten rules" of the system.

Step 3: Technical Debt Audit#

Use Replay’s AI Automation Suite to run a technical debt audit on the extracted flows. Identify which parts of the legacy system are redundant and can be retired rather than migrated.

Step 4: Component and Test Generation#

Generate the React components and, crucially, the End-to-End (E2E) tests. Replay uses the recording to create Playwright or Cypress tests that ensure the new system behaves exactly like the old one.

Step 5: Incremental Deployment#

Use the Strangler Fig pattern to deploy the new components alongside the legacy system. Because Replay has already generated the API bridge, the new React components can live inside the legacy shell during the transition.

Frequently Asked Questions#

How long does legacy extraction take?#

While manual documentation takes 40+ hours per screen, Replay reduces this to roughly 4 hours. A complex enterprise module can typically be fully documented and extracted into React components within 3 to 5 business days.

What about business logic preservation?#

This is the core strength of Visual Reverse Engineering. By recording the actual execution of the system, we capture the logic as it is experienced by the user and the server. Replay extracts the conditional logic (e.g., "If field A is X, then field B must be Y") and embeds it into the generated TypeScript code.

Does Replay support mainframe or desktop apps?#

Yes. Because Replay uses visual recording and network interception, it can be used to document and extract logic from web-based legacy systems (ASP.NET, Silverlight, JSP), desktop applications via terminal emulation, and even mainframe interfaces.

How does this handle technical debt?#

Replay identifies "Dead Logic"—code paths that are never triggered during real-world usage. By focusing on what users actually do, you can avoid migrating 20-30% of your legacy codebase that is no longer relevant, significantly reducing your future maintenance burden.

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