The 48-Hour Assessment: Rapid Legacy Inventory via Video

The average enterprise rewrite takes 18 to 24 months, yet 70% of these projects fail to meet their original objectives or budget. The primary reason isn't a lack of engineering talent; it’s a lack of understanding. Most organizations are operating "black box" systems where the original architects have long since departed, leaving behind millions of lines of undocumented code and a $3.6 trillion global technical debt mountain.

Traditional discovery—what I call "software archaeology"—is a manual, error-prone process that consumes months of senior architect time. We have seen teams spend 40 hours manually documenting a single complex legacy screen. With Replay, that timeline drops to 4 hours.

TL;DR: The 48-Hour Assessment uses visual reverse engineering to transform legacy user workflows into documented React components and API contracts, reducing discovery time by 70%.

The Failure of "Archaeology-First" Modernization#

67% of legacy systems lack any form of up-to-date documentation. When a VP of Engineering initiates a modernization project in a regulated industry like Financial Services or Healthcare, the first instinct is to assign a team to "read the code."

This is a strategic mistake.

Reading 15-year-old legacy code to understand business logic is like trying to reconstruct a building by looking at a pile of crushed bricks. You see the components, but you lose the intent. The "source of truth" isn't the code—it's the behavior of the system in the hands of the user.

The Cost of Manual Discovery#

Defining the 48-Hour Assessment#

The 48-Hour Assessment is a focused sprint designed to move an enterprise from "zero visibility" to a "documented roadmap." Instead of interviewing developers who might not remember why a specific validation logic exists, we record the actual workflow.

Replay captures the interaction layer, the network calls, and the state changes. It then uses AI-driven automation to reverse-engineer these recordings into modern technical assets.

💰 ROI Insight: By shifting from manual code audits to video-based extraction, enterprise teams typically save 70% of the initial modernization budget, allowing those funds to be redirected toward feature development rather than discovery.

The 3-Step Execution Framework#

Step 1: Workflow Mapping and Recording#

Identify the "Golden Paths" of your application. In an insurance claims system, this might be the "First Notice of Loss" (FNOL) workflow. A subject matter expert (SME) performs the task while Replay records the session. Unlike a standard screen recording, Replay captures the underlying metadata, DOM structures, and API traffic.

Step 2: Visual Reverse Engineering & Extraction#

The Replay engine analyzes the recording. It identifies recurring UI patterns and maps them to a centralized Library (Design System). It looks at the data flowing between the frontend and the legacy backend to generate API Contracts.

Step 3: Blueprint Generation#

The final output is a Blueprint—a functional, editable representation of the legacy screen in modern React. This isn't just a "screenshot to code" conversion; it's a structural reconstruction that preserves business logic.

typescript
// Example: Replay-generated React component from a legacy banking terminal
// Logic preserved: Interest rate calculation and validation state
import React, { useState, useEffect } from 'react';
import { LegacyDataGrid, ValidationAlert } from '@internal/design-system';

export const LoanOriginationModule = ({ accountId }: { accountId: string }) => {
  const [rate, setRate] = useState<number>(0);
  const [isEligible, setIsEligible] = useState<boolean>(false);

  // Business logic extracted from legacy network trace
  const calculateRiskAdjustment = (baseRate: number) => {
    return baseRate > 5.5 ? baseRate + 0.25 : baseRate;
  };

  return (
    <div className="p-6 bg-white rounded-lg shadow">
      <h2 className="text-xl font-bold">Loan Assessment</h2>
      <LegacyDataGrid 
        source={`/api/v1/accounts/${accountId}/history`} 
        onRowSelect={(data) => setRate(calculateRiskAdjustment(data.baseRate))}
      />
      {rate > 7.0 && <ValidationAlert message="High Risk Profile Detected" />}
    </div>
  );
};

Moving from Black Box to Documented Codebase#

One of the greatest fears for a CTO is the "Black Box" effect—where a system works, but nobody knows how. This leads to "fear-based development," where teams refuse to touch core modules for fear of breaking undocumented dependencies.

Replay's Flows feature visualizes the architecture of these black boxes. By recording multiple user sessions, Replay maps the interdependencies between screens and services.

⚠️ Warning: Attempting a "Big Bang" rewrite without a visual inventory usually results in "Feature Parity Debt," where the new system fails because it missed 10% of the hidden edge cases that the legacy system handled silently.

Technical Debt Audit#

As part of the 48-hour window, Replay generates a Technical Debt Audit. This report categorizes legacy components into:

1. •Redundant: Code paths never hit during user recordings.
2. •Critical Logic: High-complexity areas that require manual oversight during migration.
3. •Commodity UI: Standard forms and tables that can be 100% automated.

Comparison of Modernization Strategies#

When deciding how to handle the inventory from your 48-Hour Assessment, consider the following technical paths:

Security and Compliance in Regulated Environments#

For our clients in Government, Telecom, and Healthcare, security isn't an afterthought—it's the barrier to entry. Performing an assessment on sensitive systems requires a platform that respects data sovereignty.

Replay is built for these environments:

• •SOC2 Type II & HIPAA Ready: Ensuring data privacy for patient and financial records.
• •On-Premise Deployment: For air-gapped environments or strict internal data policies, Replay can run entirely within your VPC.
• •PII Masking: Automated redaction of sensitive user data during the recording and extraction phase.

📝 Note: In a recent engagement with a Tier-1 bank, Replay identified over 400 orphaned API endpoints that were still active but hadn't been touched by a user in three years. Removing these reduced the attack surface significantly before a single line of new code was written.

Generating API Contracts and E2E Tests#

The 48-Hour Assessment doesn't just stop at the UI. Because Replay sits between the user and the server during the recording phase, it observes the exact data shapes required by the legacy backend.

It automatically generates OpenAPI (Swagger) specifications, which serve as the bridge for your new frontend. Furthermore, it generates Playwright or Cypress E2E tests based on the recorded user flow, ensuring that your modernized version maintains functional parity.

yaml
# Generated API Contract from Replay Extraction
openapi: 3.0.0
info:
  title: Legacy Claims API
  version: 1.0.0
paths:
  /claims/{claimId}/validate:
    post:
      summary: Extracted from FNOL Workflow
      parameters:
        - name: claimId
          in: path
          required: true
          schema:
            type: string
      responses:
        '200':
          description: Validation successful
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/ClaimStatus'

Frequently Asked Questions#

How long does the full legacy extraction take?#

While the initial technical inventory and assessment take 48 hours, a full extraction of a complex enterprise module (approx. 50-100 screens) typically takes 2 to 4 weeks. This is a massive improvement over the 18-month average for manual rewrites.

What about business logic preservation?#

Replay captures business logic by observing state transitions and network payloads. While it cannot "see" code that never executes (dead code), it perfectly captures the logic that actually powers your business today. Our AI Automation Suite then assists architects in refactoring this observed logic into clean, modern TypeScript.

Does this replace my existing developers?#

No. Replay is a "force multiplier." It removes the "grunt work" of manual documentation and UI scaffolding, allowing your senior architects to focus on high-level system design and complex integration challenges rather than re-typing form fields and CSS.

Can Replay handle mainframe or terminal-based systems?#

Yes. Through visual analysis and terminal stream capture, Replay can map "green screen" workflows into modern web-based components, effectively bridging the gap between 1980s infrastructure and 2024 user expectations.

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