The ROI of Modernization: How One Telecom Cut Maintenance Spend by 45% in 12 Months

The global technical debt crisis has reached $3.6 trillion, and for most Tier-1 telecommunications providers, this isn't an abstract figure—it’s a daily operational tax. When a major North American telecom realized they were spending 80% of their engineering budget on "keeping the lights on" for a 15-year-old billing and provisioning system, they faced a classic architectural crossroads: endure the "Big Bang" rewrite that 70% of enterprises fail to complete, or continue bleeding cash into a system that no one fully understood.

The reality of legacy systems is that they are rarely "broken"; they are simply undocumented. With 67% of legacy systems lacking any up-to-date documentation, engineers are forced into "software archaeology"—spending weeks reading minified JS or obscure COBOL just to change a button color.

By pivoting from manual archaeology to visual reverse engineering with Replay, this telecom didn't just modernize; they slashed their maintenance spend by 45% in a single year.

TL;DR: Modernizing legacy systems doesn't require a high-risk "Big Bang" rewrite; by using visual reverse engineering with Replay, enterprises can reduce maintenance spend by 45% and cut modernization timelines from years to weeks.

The Massive Cost of Doing Nothing#

The "maintenance trap" is a silent killer of innovation. In the telecom sector, where agility is required to compete with lean MVNOs and digital-native services, legacy drag is a competitive liability.

Most CTOs underestimate the ROI of modernization because they only look at the cost of the project, not the cost of the status quo. Consider these industry benchmarks:

• •The Documentation Gap: 67% of legacy systems have no reliable technical documentation.
• •The Rewrite Failure Rate: 70% of enterprise rewrites fail or significantly exceed their 18-24 month timelines.
• •The Manual Labor Tax: It takes an average of 40 hours of manual engineering effort to document, map, and rebuild a single complex legacy screen.

Why Traditional Rewrites Are ROI Poison#

Traditional modernization fails because it relies on human memory and manual extraction. When you ask a senior dev to "rewrite the billing module," they spend 90% of their time trying to figure out why the original developer added a specific

statement in 2009.

This is what we call the "Black Box" problem. The business logic is trapped in the execution, not the code. Replay changes this by using the video as the source of truth. By recording a real user workflow, Replay captures every state change, every API call, and every UI transition. It turns a black box into a documented codebase.

💰 ROI Insight: Reducing the time-per-screen from 40 hours to 4 hours (a 90% reduction) allows a team of 10 engineers to accomplish in 2 months what would normally take 18 months.

Step-by-Step: The Replay Modernization Framework#

To achieve a 45% reduction in maintenance spend, the telecom followed a structured, four-step process that moved them from "archaeology" to "automation."

Step 1: Technical Debt Audit & Assessment#

Before writing a single line of React, you must understand the surface area. Replay’s AI Automation Suite scans the legacy environment to identify dead code paths and high-complexity modules.

• •Identify the "hot paths" (most used features).
• •Map existing API dependencies.
• •Audit security vulnerabilities in legacy libraries.

Step 2: Visual Recording of Workflows#

Instead of reading 50,000 lines of spaghetti code, the team recorded actual user workflows within the legacy billing application.

• •Record the "Happy Path" (User pays bill successfully).
• •Record "Edge Cases" (User has expired credit card, user is in a restricted region).
• •Replay captures the DOM state, network requests, and business logic triggers in real-time.

Step 3: Automated Extraction to React#

This is where the magic happens. Replay takes those recordings and generates clean, modular React components and TypeScript definitions.

typescript
// Example: Generated component from Replay extraction 
// This preserves the exact business logic captured during the session recording.

import React, { useState, useEffect } from 'react';
import { LegacyBillingService } from './services/billing';

interface BillingState {
  balance: number;
  currency: string;
  isOverdue: boolean;
}

export const ModernizedBillingPanel: React.FC<{ userId: string }> = ({ userId }) => {
  const [accountData, setAccountData] = useState<BillingState | null>(null);

  // Logic extracted from legacy session: handles specific telecom grace periods
  const checkOverdueStatus = (daysPastDue: number) => {
    return daysPastDue > 15; // Extracted business rule
  };

  useEffect(() => {
    async function loadData() {
      const data = await LegacyBillingService.fetchAccount(userId);
      setAccountData({
        ...data,
        isOverdue: checkOverdueStatus(data.daysPastDue)
      });
    }
    loadData();
  }, [userId]);

  if (!accountData) return <LoadingSpinner />;

  return (
    <div className="p-6 bg-white rounded-lg shadow-md">
      <h2 className="text-xl font-bold">Account Balance</h2>
      <p className={`text-2xl ${accountData.isOverdue ? 'text-red-600' : 'text-green-600'}`}>
        {accountData.currency}{accountData.balance}
      </p>
      {accountData.isOverdue && (
        <div className="mt-4 p-2 bg-red-100 text-red-800">
          ⚠️ Action Required: Account is in grace period.
        </div>
      )}
    </div>
  );
};

Step 4: API Contract Generation & E2E Testing#

One of the biggest risks in modernization is breaking the "contract" between the frontend and the backend. Replay automatically generates API contracts based on the network traffic captured during recording.

⚠️ Warning: Never assume your legacy API documentation is correct. In 90% of cases, the actual JSON response differs from the 5-year-old Swagger doc. Replay uses the actual traffic to build the contract.

json
// Auto-generated API Contract from Replay Recording
{
  "endpoint": "/api/v1/provisioning/status",
  "method": "GET",
  "expected_response": {
    "subscriber_id": "string",
    "status": "enum[ACTIVE, SUSPENDED, PENDING]",
    "last_billing_cycle": "ISO8601_Date",
    "features": "array<string>"
  },
  "observed_latency_p95": "142ms"
}

How the 45% Savings Was Realized#

The telecom's ROI wasn't just about faster coding. It was about the elimination of "Wasteful Engineering."

1. •Elimination of "Discovery" Time: Engineers no longer spent Mondays trying to understand how a feature worked. They just watched the Replay Flow.
2. •Reduced Regression Cycles: Because Replay generates E2E tests based on the recording, the QA cycle was cut from 3 weeks to 2 days.
3. •Onboarding Speed: New hires were productive in 48 hours because the "Blueprints" provided a visual map of the entire architecture.
4. •Infrastructure Optimization: By moving from a monolithic JSP architecture to modern React components served via CDN, they reduced server costs by 30%.

📝 Note: In regulated industries like Telecom and Finance, Replay's ability to run On-Premise is critical. You get the power of AI-driven extraction without your sensitive customer data ever leaving your VPC.

Architectural Deep Dive: The Library and the Flows#

Replay provides three core pillars that replace the traditional "Wiki that no one updates":

The Library (Design System)#

As screens are recorded, Replay identifies recurring UI patterns. It extracts these into a centralized Design System. Instead of having 50 different "Submit" buttons across 10 legacy apps, you get one documented React component that serves them all.

Flows (Architecture)#

Flows provide a visual map of the user's journey through the system. For the telecom, this meant mapping the "New Subscriber Activation" flow, which touched seven different microservices. Seeing this visually allowed architects to identify bottlenecks that were previously invisible in the code.

Blueprints (The Editor)#

Blueprints allow architects to tweak the extracted logic before it's committed to the new repository. It’s a bridge between the "as-is" legacy state and the "to-be" modern state.

The Future Isn't Rewriting—It's Understanding#

We have to stop treating legacy systems as "technical debt" to be erased and start treating them as "institutional knowledge" to be harvested. The reason the telecom succeeded where others failed is that they didn't try to outsmart the legacy system; they used Replay to understand it.

The ROI of modernization is found in the delta between manual labor and automated insight. When you can move a screen from a black-box legacy environment to a modern, documented React component in 4 hours instead of 40, the financial argument for modernization becomes undeniable.

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Frequently Asked Questions#

How long does legacy extraction take with Replay?#

While a manual extraction takes 40+ hours per screen, Replay users typically see a fully documented React component and API contract in under 4 hours. For a standard enterprise module of 20 screens, you can move from "Legacy" to "Modern" in about two weeks of engineering time.

What about business logic preservation?#

This is Replay's core strength. Because we record the execution of the code, we capture the logic that is often missed in static analysis. If a specific edge case triggers a UI change, Replay captures that state transition and reflects it in the generated TypeScript logic.

Does Replay support regulated environments?#

Yes. Replay is built for Financial Services, Healthcare, and Telecom. We are SOC2 compliant, HIPAA-ready, and offer an On-Premise deployment model so that your source code and session data stay within your secure perimeter.

Can we modernize incrementally?#

Absolutely. Most of our clients use the "Strangler Fig" approach—modernizing one high-value workflow at a time. Replay makes this easier by generating the glue code (API wrappers) needed for the new React components to talk to the old backend.

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