Telecom Billing Migration: Moving from Mainframe to Cloud Without Losing a Cent

The average telecom billing system is a digital palimpsest—layers of COBOL, PL/I, and obscure middleware stacked over forty years. When a Tier-1 telco attempts to migrate these systems to the cloud, they aren't just moving code; they are moving the financial nervous system of an enterprise. One miscalculated rounding rule or a dropped event trigger doesn't just result in a bug; it results in millions of dollars in revenue leakage or regulatory fines.

TL;DR: Modernizing telecom billing fails when treated as a code rewrite; success requires Visual Reverse Engineering to extract undocumented business logic into modern React components and API contracts, reducing migration timelines by 70%.

The $3.6 Trillion Technical Debt Trap#

Telecom operators are currently sitting on a massive portion of the $3.6 trillion global technical debt. For a VP of Engineering, the "Big Bang" rewrite is the most dangerous path. Statistics show that 70% of legacy rewrites fail or significantly exceed their timelines. In the telecom sector, the average enterprise rewrite timeline stretches to 18–24 months, often resulting in a "feature-parity" chase that never ends because the legacy system is a moving target.

The core problem is what I call "Software Archaeology." Most legacy billing systems lack documentation (67% of systems, according to industry benchmarks). The original architects have retired, and the "source of truth" is no longer the code—it’s the behavior of the system as seen by the users who navigate green-screen terminal emulators or aging Java applets.

Why Manual Extraction is a Career Killer#

The traditional way to modernize a billing screen involves a business analyst sitting with an operator, taking screenshots, and writing a 50-page functional requirement document (FRD). A developer then spends an average of 40 hours per screen trying to translate those requirements into a modern UI and backend service.

⚠️ Warning: Manual documentation is the primary source of "logic drift." If the developer misses a single conditional logic gate buried in a legacy sub-routine, the billing calculation will be off.

With Replay, we change the source of truth. Instead of an FRD, the source of truth is a recording of the actual workflow. By recording the legacy system in action, Replay’s AI Automation Suite extracts the underlying logic, state changes, and API requirements. This reduces the time per screen from 40 hours to just 4 hours.

The Replay Architecture: From Black Box to React#

Replay doesn't just "scrape" a screen. It understands the intent. Our platform consists of four pillars designed for the complexity of telecom environments:

1. •Library (Design System): Centralizes the extracted components to ensure consistency across the new billing portal.
2. •Flows (Architecture): Maps the end-to-end user journey—from "Adjust Balance" to "Generate Invoice."
3. •Blueprints (Editor): The workspace where architects refine the generated React code and API contracts.
4. •AI Automation Suite: The engine that identifies technical debt and suggests modern architectural patterns.

Step 1: Recording the Workflow#

In a billing environment, you start by recording high-value workflows: invoice disputes, plan upgrades, and payment processing. Replay captures the DOM state, network calls, and user interactions.

Step 2: Extraction and Component Generation#

Replay analyzes the recording and generates functional React components. It doesn't just copy the HTML; it identifies patterns. If the legacy system uses a specific validation for international roaming charges, Replay captures that logic.

typescript
// Example: Generated component from Replay video extraction
// This component preserves the legacy validation logic for billing adjustments
import React, { useState, useEffect } from 'react';
import { Button, Input, Alert } from '@/components/ui';

export function BillingAdjustmentModule({ subscriberId, legacyCode }) {
  const [adjustment, setAdjustment] = useState(0);
  const [error, setError] = useState(null);

  // Replay extracted this specific rounding logic from the mainframe behavior
  const validateAdjustment = (value: number) => {
    if (value > 500 && legacyCode === 'PREPAID_V3') {
      return "Supervisor approval required for adjustments over $500";
    }
    return null;
  };

  const handleApply = () => {
    const validationError = validateAdjustment(adjustment);
    if (validationError) {
      setError(validationError);
      return;
    }
    // API Contract generated by Replay based on recorded network traffic
    submitAdjustment({ id: subscriberId, amount: adjustment });
  };

  return (
    <div className="p-4 border rounded-lg bg-white shadow-sm">
      <h3>Apply Billing Adjustment</h3>
      <Input 
        type="number" 
        onChange={(e) => setAdjustment(Number(e.target.value))} 
        placeholder="Enter amount"
      />
      {error && <Alert variant="destructive">{error}</Alert>}
      <Button onClick={handleApply}>Apply to Account</Button>
    </div>
  );
}

💰 ROI Insight: By automating the generation of these components, enterprise teams save an average of 36 hours per screen. For a billing system with 200 screens, that’s 7,200 hours of senior engineering time saved—roughly $1.2M in labor costs.

Preserving Business Logic: The "Cents" Problem#

In telecom, the "cent" is king. Legacy systems often have idiosyncratic ways of handling tax calculations or pro-rated credits. Replay’s Blueprints allow architects to see the "Before" (Legacy) and "After" (Modern) side-by-side, ensuring that the API contracts generated match the legacy output exactly.

Step 3: API Contract Generation#

Replay looks at the data flowing in and out of the legacy system during the recording and generates an OpenAPI/Swagger specification. This allows your backend team to build microservices that are "plug-and-play" compatible with the newly generated frontend.

yaml
# Generated API Contract from Replay Flow
openapi: 3.0.0
info:
  title: Telecom Billing Adjustment API
  version: 1.0.0
paths:
  /adjustments:
    post:
      summary: Apply adjustment based on legacy business rules
      requestBody:
        content:
          application/json:
            schema:
              type: object
              properties:
                subscriberId: { type: string }
                amount: { type: number }
                legacyCode: { type: string }
      responses:
        '200':
          description: Adjustment applied successfully

Built for Regulated Environments#

Telecom is a heavily regulated industry. You cannot simply send billing data to a public cloud AI for analysis. Replay is built for these constraints:

• •SOC2 & HIPAA Ready: We adhere to the highest security standards.
• •On-Premise Available: For sensitive billing environments, Replay can run entirely within your private cloud or air-gapped data center.
• •Technical Debt Audit: Before you write a single line of new code, Replay provides an audit of the legacy system, identifying which parts are redundant and which are critical for the migration.

📝 Note: Replay does not require access to your legacy source code. It works by observing the output and interaction of the system, making it perfect for systems where the source code is lost or unreadable.

The Migration Roadmap: From 18 Months to 8 Weeks#

How do we achieve these timelines? By eliminating the "Discovery" phase that usually takes 6 months.

1. •Assessment (Week 1): Use Replay to record all primary and secondary workflows in the legacy billing system.
2. •Extraction (Weeks 2-3): Replay generates the React component library and initial API contracts.
3. •Refinement (Weeks 4-5): Developers use Replay Blueprints to refine business logic and integrate with modern backend services.
4. •Testing (Weeks 6-7): Replay generates E2E tests based on the original recordings to ensure the new system behaves exactly like the old one.
5. •Deployment (Week 8): Final cutover of the first module (e.g., Customer Care Billing View).

Frequently Asked Questions#

How does Replay handle mainframe systems without a web interface?#

Replay can interface with terminal emulators and Citrix-delivered applications. If a human can see it and interact with it, Replay can record the workflow and extract the structural patterns and logic required to rebuild it in React.

What about business logic preservation?#

This is our core strength. Because Replay records the behavior of the system, it captures the actual outcomes of complex logic. We generate the modern code to replicate those outcomes, and our "Technical Debt Audit" flags areas where the legacy logic is inconsistent, allowing your architects to make informed decisions.

Does this replace my developers?#

No. It empowers them. Instead of spending months on tedious "code archaeology" and manual UI building, your senior engineers spend their time on high-value architecture and integration. Replay handles the 70% of the work that is repetitive and error-prone.

Is the generated code maintainable?#

Yes. Replay generates clean, documented React code using your organization's specific coding standards and design system. It is not "spaghetti code"; it is a professional-grade codebase that your team will own and maintain.

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