How a Simple Call Stack Optimization Saved Us 500K API Calls Monthly

Introduction

Fourteen years in full-stack development—spanning Node.js backends, NestJS APIs, Angular dashboards, and React Native apps—have taught me that user frustration can be the ultimate motivator. In a React Native app with tens of thousands of users, we saw ~500k API calls failing monthly—not because our servers choked, but because app-level errors like bad internet or device crashes left users stuck. Progress vanished, data didn’t sync, and complaints piled up. After years of refining a callstack worker to retry those fails and save the day, I’ve open-sourced it as @radoslawfabisiak/react-native-callstack.

Here’s how it turned ~500k errors into results, with code and the story behind it.

The User Pain Point

Imagine a user—part of our thousands-strong base—trying to load data with fetchItems. Their signal drops, the call fails before reaching our servers, and they’re left staring at an error. They retry, nothing saves, and frustration boils—~500k such fails monthly across users. Or take completeTask: a user finishes a task, but a device crash wipes it out—no sync, no record. These weren’t server issues—they were app-side disasters, and users paid the price.

Why Caches, Queues, and Workers Missed the Mark

Caches like Redux? They store successes, not failures—useless when calls die on-device. Server-side queues like Bull? They need a backend ping—these never got there. Background workers? They retry server fails, not app-level chaos: bad Wi-Fi, app crashes, OS quirks. Without a fix, ~500k calls failed monthly—users lost data, progress vanished, and support tickets spiked. We needed a device-side savior.

The Callstack Worker Solution

Enter @radoslawfabisiak/react-native-callstack—a worker we built years ago to rescue those ~500k failed calls monthly. It runs once, queues app-level fails, and retries them until they succeed, using AsyncStorage to persist across restarts and a custom functionMap for your APIs. Features:

• App-Level Recovery: Catches fails before server contact.
• Deduplication: One call per type/payload—avoids retry clutter.
• Persistence: Survives crashes, keeps data alive.
• Custom Mapping: Handles payloads (e.g., itemId or user, task, points).

This turned ~500k monthly errors into results—users got their data, frustration faded.

How to Use @radoslawfabisiak/react-native-callstack

Let’s set it up. Install:

npm install @radoslawfabisiak/react-native-callstack

Setup as a Global Instance

Define it in callstack.js:

import ReactNativeCallstack from '@radoslawfabisiak/react-native-callstack';
import { fetchItems, completeTask } from './api';

export const callstack = new ReactNativeCallstack({
  functionMap: {
    fetchItems: async () => await fetchItems(),
    completeTask: async ({ user, task, points }) => await completeTask(user, task, points)
  }
});

Initialize in Your Main Component

Trigger it in Main.js:

import React, { useEffect } from 'react';
import { callstack } from './callstack';

function Main() {
  useEffect(() => {
    callstack.initialize().catch(err => console.error('Callstack init failed:', err));
  }, []);

  return <YourApp />;
}

export default Main;

Rescue Failed Calls

Catch errors anywhere:

import { callstack } from './callstack';
import { fetchItems } from './api';

async function loadItems() {
  try {
    const result = await fetchItems();
    if (!result.success) throw new Error('Bad response');
    return result;
  } catch (error) {
    callstack.add({
      type: 'fetchItems',
      payload: {},
      error: new Error('Network')
    });
  }
}

For multi-arg calls:

import { completeTask } from './api';
import { callstack } from './callstack';

async function finishTask(user, task, points) {
  try {
    const result = await completeTask(user, task, points);
    if (!result.success) throw new Error('Device crash');
    return result;
  } catch (error) {
    callstack.add({
      type: 'completeTask',
      payload: { user, task, points },
      error
    });
  }
}

Customize error logging:

callstack.add({
  type: 'fetchItems',
  payload: {},
  error,
  onError: ({ attempts, error }) => console.log(`Retried ${attempts}x:`, error)
});

It’s plug-and-play—queue fails, it retries, data sticks.

The Rescue: ~500k Fails Turned to Wins

Before this worker, thousands of users hit errors monthly—~500k failed calls from bad signals, crashes, quirks. Progress—like task completions—vanished; users fumed. After:

• Retries: Queued ~500k fails, retried every 500ms—most succeeded.
• Deduplication: One call per type/payload—cut repeat failures.
• Persistence: Crashes didn’t wipe queues—data held firm.

Support tickets dropped, users kept their results—e.g., tasks synced, items loaded—~500k frustrations eased monthly.

Why Open-Source It?

This worker rescued ~500k failed calls monthly—user relief, not just server savings—so I open-sourced it as @radoslawfabisiak/react-native-callstack. It’s my gift to the React Native community—install it, save your users’ progress.

Years of grit—crashes, dropouts, user pleas. AI can’t feel that; ~500k saves monthly is my story, now yours.

Need Help?

Reach me on LinkedIn: https://www.linkedin.com/in/radek-fabisiak/.

Conclusion

@radoslawfabisiak/react-native-callstack is on npm—grab it, queue fails, keep users happy. From ~500k lost retries to success, it’s been our fix for years, now yours.

Fork it on GitHub, tweak it—let’s ease mobile woes together.