Microservices vs Monolith: What Visual Extraction Reveals About Your Architecture

The $3.6 trillion global technical debt crisis isn't caused by a lack of talent; it’s caused by a lack of visibility. Most Enterprise Architects are making architectural decisions—like whether to move from a monolith to microservices—based on outdated documentation, tribal knowledge, and "archaeology" sessions that consume months of high-value engineering time.

When 70% of legacy rewrites fail or exceed their timelines, the problem isn't the destination; it's the map. We treat legacy systems as black boxes, assuming that a "Big Bang" rewrite is the only way out. It isn't. The future of modernization isn't rewriting from scratch—it’s understanding exactly what you already have through Visual Reverse Engineering.

TL;DR: Visual extraction transforms the "Microservices vs Monolith" debate from a theoretical architectural argument into a data-driven migration by using real user workflows to map dependencies, generate code, and define service boundaries in days rather than years.

The Architecture Lie: Idealized vs. Actual#

In most enterprises, the "Architecture Diagram" is a work of fiction. You might think you have a clean monolith or a decoupled microservices environment, but the reality is often a "distributed monolith" where services are tightly coupled through undocumented side effects.

Statistics show that 67% of legacy systems lack any meaningful documentation. When you attempt to modernize these systems manually, it takes an average of 40 hours per screen just to document and replicate the logic. With Replay, that time is cut to 4 hours.

Comparing Modernization Strategies#

What Visual Extraction Reveals#

Visual extraction via Replay works by recording real user workflows. As a user interacts with the legacy system, Replay captures the DOM changes, network requests, and state transitions. This "video as a source of truth" allows us to see the architecture as it actually functions, not as it was intended ten years ago.

1. Hidden Dependency Chains#

In a monolith, a simple "Submit Order" button might trigger fourteen different database writes across five different domains. Visual extraction identifies these chains instantly. If you are moving to microservices, these are your "bounded contexts." If you don't identify them before you start coding, you will end up with a network-latency nightmare.

2. Dead Code and Ghost Logic#

Enterprise systems are littered with "just in case" logic. Manual audits often result in developers porting code that hasn't been executed since 2014. Visual extraction proves exactly which paths are active.

💰 ROI Insight: By eliminating the "archaeology" phase, enterprises save an average of 70% on modernization timelines. Moving a single complex module from 18 months to 3 weeks changes the entire financial profile of a digital transformation project.

From Video to React: The Technical Bridge#

Replay doesn't just show you a video; it generates the actual code. It looks at the legacy output and produces documented React components and API contracts. This allows you to "modernize without rewriting" by extracting the UI and logic into a modern stack (React/TypeScript) while keeping the business rules intact.

typescript
// Example: Component extracted via Replay Blueprints
// This component preserves legacy business logic while using modern hooks
import React, { useState, useEffect } from 'react';
import { LegacyAPI } from '@internal/legacy-bridge';

export const InsuranceClaimPortal: React.FC<{ claimId: string }> = ({ claimId }) => {
  const [status, setStatus] = useState<'idle' | 'loading' | 'error'>('idle');
  const [data, setData] = useState<any>(null);

  // Replay identified this specific sequence from the network trace
  const handleValidation = async () => {
    const isValid = await LegacyAPI.validatePolicy(claimId);
    if (isValid) {
      // Logic extracted from observed user workflow
      triggerWorkflowSync();
    }
  };

  return (
    <div className="modern-container shadow-lg p-6">
      <h2 className="text-xl font-bold">Claim Status: {data?.status}</h2>
      <button 
        onClick={handleValidation}
        className="bg-blue-600 text-white px-4 py-2 rounded"
      >
        Validate Coverage
      </button>
    </div>
  );
};

Mapping the Microservices Boundary#

The biggest challenge in the "Microservices vs Monolith" debate is where to draw the line. If you draw it incorrectly, you increase complexity without gaining scalability.

Replay’s Flows feature visualizes the architecture by mapping every screen to its underlying API calls. When you record a workflow, Replay generates an API contract (OpenAPI/Swagger) automatically.

Step 1: Record the Workflow#

A subject matter expert (SME) performs a standard task in the legacy system—for example, "Onboarding a New Patient" in a healthcare CRM.

Step 2: Analyze the Trace#

Replay’s AI Automation Suite analyzes the network traffic. It identifies that the "Onboarding" flow hits three distinct legacy endpoints:

, , and .

Step 3: Define the Service#

Instead of guessing, the Architect sees that

has zero overlap with . This is a natural microservice boundary.

Step 4: Generate the Contract#

Replay generates the modern API contract required to replace the legacy backend.

yaml
# Generated API Contract from Replay Extraction
openapi: 3.0.0
info:
  title: Patient Onboarding Service
  version: 1.0.0
paths:
  /v1/patient/onboard:
    post:
      summary: Extracted from Legacy CRM Workflow
      responses:
        '200':
          description: Successful onboarding
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Patient'

⚠️ Warning: Attempting to split a monolith without first mapping the data flow via visual extraction leads to "Circular Dependencies," the leading cause of microservice project abandonment.

The Cost of Manual Modernization#

The "Standard" enterprise rewrite timeline is 18 months. Why?

1. •Month 1-4: Discovery and Documentation (Manual).
2. •Month 5-8: Environment Setup and "Hello World" in the new stack.
3. •Month 9-15: Porting logic and finding out the documentation was wrong.
4. •Month 16-18: Bug fixing the "edge cases" that were missed during discovery.

Replay compresses months 1-15 into a matter of days. By recording the "edge cases" as they happen in the UI, the "documentation" is generated automatically and with 100% accuracy.

💡 Pro Tip: Use Replay's Library (Design System) feature to identify duplicate UI patterns across your monolith. Most legacy systems have 5-10 different versions of the same "Date Picker" or "Data Grid." Consolidating these during extraction reduces your future maintenance burden by 30%.

Built for Regulated Environments#

Modernizing systems in Financial Services, Healthcare, or Government isn't just a technical challenge; it's a compliance challenge. You cannot simply send data to a public AI or cloud service.

Replay is built for these constraints:

• •SOC2 & HIPAA Ready: Data privacy is baked into the extraction process.
• •On-Premise Available: Keep your source code and recordings within your own firewall.
• •Technical Debt Audit: Automatically generate reports that show stakeholders exactly where the risk lies.

Frequently Asked Questions#

How long does legacy extraction take?#

While a manual rewrite takes 18-24 months, a Replay-assisted modernization typically takes 2-8 weeks per module. We see a consistent 70% reduction in time-to-production because the "Discovery" phase is automated.

What about business logic preservation?#

Replay records the inputs, outputs, and state changes of the legacy system. Our AI Automation Suite then suggests React/TypeScript implementations that mirror that logic. Because we generate E2E tests based on the original recording, you can verify that the new system behaves exactly like the old one.

Can Replay handle mainframes or terminal-based systems?#

Yes. If it has a UI (web-based, desktop, or terminal emulator), Replay can record the workflow. Our platform is designed to bridge the gap between "Green Screen" logic and modern React architectures.

Does this replace my developers?#

No. It empowers them. Instead of spending 80% of their time reading 15-year-old COBOL or Java 1.4 code, they spend their time building new features in a modern React environment. Replay handles the "grunt work" of reverse engineering.

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