Refactoring Legacy AJAX Calls to GraphQL: A Visual Behavioral Approach

The $3.6 trillion global technical debt isn't just a number on a balance sheet; it’s the sound of a thousand

calls failing in a production environment no one fully understands. For most enterprise architects, the nightmare isn't the new feature request—it's the 15-year-old dashboard that relies on a tangled web of undocumented jQuery requests, global state mutations, and "spaghetti" endpoints.

When you are tasked with refactoring legacy ajax calls, you aren't just changing a transport layer. You are performing archeology. You are digging through layers of "temporary fixes" from developers who haven't worked at the company since the Obama administration. According to Replay’s analysis, 67% of these legacy systems lack any form of usable documentation, leaving modern teams to guess at data shapes and side effects.

TL;DR: Refactoring legacy AJAX calls to GraphQL manually takes roughly 40 hours per screen and has a 70% failure rate in enterprise settings. By using Replay, a visual reverse engineering platform, teams can record user workflows to automatically map data dependencies, reducing the migration timeline from 18 months to a few weeks. This post explores how to transition from brittle

text

XMLHttpRequest

patterns to type-safe GraphQL using visual behavioral analysis.

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The Hidden Cost of Refactoring Legacy AJAX Calls#

The traditional approach to modernization is the "Rip and Replace" strategy. You sit a developer down with Chrome DevTools open, tell them to click every button, and manually document every XHR request. This is not only soul-crushing; it’s inefficient.

Industry experts recommend moving toward GraphQL because it solves the two biggest sins of legacy AJAX: over-fetching and under-fetching. In a legacy environment, a single dashboard might trigger 15 separate AJAX calls to populate a user profile, a list of orders, and a permissions set. This leads to the "N+1 problem" at the UI layer, causing significant latency and a poor user experience.

However, refactoring legacy ajax calls manually is fraught with risk. If you miss a single

flag or a hidden global variable dependency in a jQuery block, you risk breaking downstream business logic that hasn't been touched in a decade.

The Manual Modernization Tax#

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What is Visual Behavioral Analysis?#

Before we dive into the implementation, we need to define the methodology.

Visual Behavioral Analysis is the process of mapping user interface interactions directly to underlying data requests by observing real-time application execution. Instead of reading code, you record the behavior of the application.

Video-to-code is the process of converting these visual recordings into functional, documented React components and data schemas.

By using Replay, you can record a user performing a specific flow—like "Onboarding a New Client"—and the platform’s AI Automation Suite extracts the exact data requirements for every UI element. It identifies that the "Client Name" label is tied to

from a specific legacy endpoint. This removes the guesswork from refactoring legacy ajax calls.

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The Legacy Mess: Anatomy of a jQuery AJAX Call#

To understand why we need GraphQL, we must look at what we’re leaving behind. Consider this typical legacy snippet found in many financial services or healthcare portals:

typescript
// The "Spaghetti" Legacy Pattern
function loadUserData(userId) {
    $.ajax({
        url: '/api/v1/get-user-details.php?id=' + userId,
        type: 'GET',
        async: true,
        success: function(response) {
            // Global state mutation - hard to track
            window.currentUser = JSON.parse(response);
            
            // Nested callback hell
            $.ajax({
                url: '/api/v1/get-user-permissions.php?role=' + window.currentUser.role,
                success: function(permissions) {
                    renderDashboard(window.currentUser, permissions);
                }
            });
        },
        error: function(err) {
            console.error("Something went wrong, but we won't tell you what.");
        }
    });
}

This code is a ticking time bomb. It relies on global variables, has no type safety, and forces the browser to wait for the first request to finish before starting the second. When refactoring legacy ajax calls like this, your goal is to collapse these multiple requests into a single, declarative GraphQL query.

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Automating the Refactoring Legacy AJAX Calls Process#

The average enterprise rewrite timeline is 18 months. Most of that time is spent in the "Discovery Phase." With Replay, we skip discovery and go straight to generation.

Step 1: Record the Workflow#

Using Replay’s "Flows" feature, a QA or Business Analyst records the legacy application in action. As they click through the UI, Replay captures the DOM mutations and the network traffic simultaneously.

Step 2: Extract the Data Schema#

Replay’s AI analyzes the recorded XHR/AJAX traffic. It identifies that while the legacy API returns 50 fields, the UI only actually uses 5. This is the foundation of your GraphQL fragment.

Step 3: Generate the React + Apollo Code#

Once the visual mapping is complete, Replay generates a modern React component using your organization's Design System (stored in the Replay Library).

Step 4: Map to GraphQL#

Instead of a mess of callbacks, you get a clean, declarative component.

tsx
// The Modern Replay-Generated Component
import React from 'react';
import { useQuery, gql } from '@apollo/client';
import { UserDashboard, LoadingSpinner, ErrorMessage } from '@/components/ui';

const GET_USER_DATA = gql`
  query GetUserData($userId: ID!) {
    user(id: $userId) {
      id
      fullName
      role
      permissions {
        canEdit
        canDelete
      }
    }
  }
`;

interface DashboardProps {
  userId: string;
}

export const ModernDashboard: React.FC<DashboardProps> = ({ userId }) => {
  const { loading, error, data } = useQuery(GET_USER_DATA, {
    variables: { userId },
  });

  if (loading) return <LoadingSpinner />;
  if (error) return <ErrorMessage message={error.message} />;

  return (
    <UserDashboard 
      user={data.user} 
      permissions={data.user.permissions} 
    />
  );
};

By refactoring legacy ajax calls into this format, you gain immediate benefits:

1. •Type Safety: TypeScript ensures you don't access properties that don't exist.
2. •Performance: One round trip to the server instead of two.
3. •Maintainability: The data requirements are co-located with the UI component.

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Why 70% of Legacy Rewrites Fail#

According to industry data, 70% of legacy rewrites fail or exceed their timeline. The primary reason is "Scope Creep" caused by hidden dependencies. When you start refactoring legacy ajax calls, you often discover that the data returned by the API is modified by a legacy utility library before it hits the screen.

Manual discovery often misses these transformations. Replay’s Visual Reverse Engineering captures the final state of the DOM, ensuring that the logic performed by those "hidden" scripts is accounted for in the new React components.

Understanding Technical Debt is the first step in avoiding these pitfalls. Many teams attempt to rewrite the backend and frontend simultaneously, which is a recipe for disaster. A better approach is to use a GraphQL wrapper (like Apollo Server or Hasura) over your legacy REST/SOAP endpoints. This allows you to modernize the frontend immediately while slowly strangling the legacy backend.

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Implementing Visual Behavioral Analysis in Regulated Environments#

For industries like Financial Services, Healthcare, and Government, security is the primary concern. You cannot simply upload recordings of sensitive data to a public cloud.

Replay is built for these environments. With SOC2 compliance, HIPAA-readiness, and On-Premise deployment options, you can perform refactoring legacy ajax calls without exposing PII (Personally Identifiable Information).

• •Financial Services: Modernize ancient core banking portals without risking transaction integrity.
• •Healthcare: Transition EHR (Electronic Health Record) systems from IE11-era AJAX to modern React.
• •Manufacturing: Update legacy ERP interfaces that run on-site servers.

Industry experts recommend that enterprise architects prioritize "observability-driven development." By observing how the legacy system actually works in the wild, you eliminate the gap between the "as-is" state and the "to-be" state.

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Advanced Strategy: Mapping Visual Flows to Blueprints#

In the Replay ecosystem, a Blueprint is the bridge between a recording and a production-ready component. When you are refactoring legacy ajax calls, the Blueprint acts as the architectural source of truth.

1. •The Recording: Captures the raw "behavior."
2. •The Blueprint: The AI-assisted editor where you refine the data mappings.
3. •The Library: The repository of your organization’s Design System components that the generated code will consume.

This workflow reduces the time spent on manual UI construction. If a screen used to take 40 hours to rebuild manually—accounting for CSS styling, state management, and API integration—Replay brings that down to 4 hours. Most of that time is spent simply reviewing the AI’s suggestions and hitting "Export."

The Future of Component Libraries lies in this automated extraction. Why build a component library from scratch when your legacy app already defines the functional requirements?

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Case Study: From 18 Months to 6 Weeks#

A major insurance provider had a legacy claims processing portal built in 2008. It was a monolith of PHP and jQuery. They estimated that refactoring legacy ajax calls and moving to a modern React/GraphQL stack would take 18 months and a team of 12 developers.

By utilizing Replay, they:

• •Recorded 45 core user flows.
• •Automatically generated the GraphQL schema based on observed network traffic.
• •Produced a documented React component library that mirrored their legacy functionality but used modern styling.
• •Result: The project was completed in 6 weeks with a team of 4.

This is the power of visual reverse engineering. It turns the "black box" of legacy code into a transparent roadmap.

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Frequently Asked Questions#

How does visual behavioral analysis handle dynamic data?#

Visual behavioral analysis doesn't just take a snapshot; it records the state changes over time. If an AJAX call is triggered by a dropdown selection, Replay captures that relationship. When refactoring legacy ajax calls, the AI identifies the parameters passed to the XHR request and maps them to GraphQL variables, ensuring the dynamic nature of the UI is preserved in the new React code.

Can Replay handle legacy systems behind a VPN or Firewall?#

Yes. Replay offers On-Premise deployment options specifically for regulated industries. This allows you to run the visual reverse engineering suite within your own secure perimeter, ensuring that sensitive data never leaves your network while you are refactoring legacy ajax calls.

Does the generated code use standard libraries?#

Absolutely. Replay generates clean, human-readable TypeScript and React code. It integrates with industry-standard libraries like Apollo Client for GraphQL, Tailwind CSS for styling, and Radix UI for primitives. There is no proprietary "lock-in" framework; the code is yours to own and maintain.

How does Replay handle undocumented or "hidden" API endpoints?#

Since Replay records actual browser behavior, it captures every single network request made by the application, including those that aren't documented in Swagger or Postman. This is crucial for refactoring legacy ajax calls, as it ensures no "hidden" data dependencies are missed during the migration to GraphQL.

What is the average ROI of using Replay for modernization?#

According to Replay's analysis, the average enterprise saves 70% in developer hours. By reducing the time per screen from 40 hours to 4 hours, organizations can redirect their senior talent toward high-value feature development instead of manual code archeology.

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Conclusion: Stop Guessing, Start Recording#

The era of manual "Rip and Replace" is over. The $3.6 trillion technical debt crisis requires a more surgical, automated approach. By refactoring legacy ajax calls using visual behavioral analysis, you bridge the gap between legacy stability and modern agility.

Replay provides the tools—Library, Flows, Blueprints, and the AI Automation Suite—to transform your modernization strategy. Don't let your legacy systems hold your innovation hostage for another 18 months.

Ready to modernize without rewriting? Book a pilot with Replay