Indie Hacker Mobile Apps · Lesson

Local Data Persistence

Learn various methods for storing and managing data locally on mobile devices, including SQLite, AsyncStorage, and shared preferences.

Local Data Persistence is a free Indie Hacker Mobile Apps lesson on CoddyKit — lesson 2 of 4. You can read the complete lesson below for free — then practise it hands-on in the browser with a built-in code editor and a 24/7 AI tutor. It is part of the Indie Hacker Mobile Apps learning path, one of 4 lessons in the course, and your progress syncs across the web and the CoddyKit app.

Why Store Data Locally?

When building mobile apps, some data needs to be available even when there's no internet connection. This is where local data persistence comes in!

It means storing information directly on the user's device, rather than always fetching it from a server.

Benefits of Local Storage

Storing data locally offers several advantages for your app:

Offline Access: Users can still use core features without internet.
Faster Performance: Retrieving data from the device is quicker than from a remote server.
Improved UX: A smoother, more responsive experience for your users.
Personalization: Saving user preferences and settings.

Simple Key-Value Pairs

One of the easiest ways to store small amounts of data is using key-value pairs. Think of it like a dictionary or a map where each piece of data has a unique name (the 'key') and its corresponding value.

This is perfect for user settings, feature flags, or simple flags like 'has seen onboarding'.

Shared Preferences (Android/iOS)

On native platforms, Android uses Shared Preferences and iOS uses UserDefaults for key-value storage. They work similarly:

Store simple data types (strings, numbers, booleans).
Are often synchronous.
Best for small amounts of non-sensitive data.

For cross-platform frameworks, you'll use an abstraction layer.

AsyncStorage: Cross-Platform K-V

For apps built with frameworks like React Native, AsyncStorage is a popular module for local key-value storage. It's an asynchronous, unencrypted, persistent key-value storage system.

Because it's asynchronous, your app won't freeze while data is being read or written.

Saving Data with AsyncStorage

Here's how you might conceptually save a user's theme preference using AsyncStorage. In a real app, AsyncStorage would be imported from a library.

// (Imagine AsyncStorage is globally available)

async function main() {
  console.log("Attempting to save user theme...");
  try {
    // In a real app, this would save to device storage.
    // await AsyncStorage.setItem('userTheme', 'dark');
    console.log("User theme 'dark' conceptually saved.");
  } catch (error) {
    console.log("Error saving data:", error.message);
  }
}

main();

Reading Data with AsyncStorage

To retrieve the saved data, you use the getItem method. It also returns a Promise, so you'll typically use await or .then().

// (Imagine AsyncStorage is globally available)

async function main() {
  console.log("Attempting to read user theme...");
  try {
    // In a real app, this would read from device storage.
    // const theme = await AsyncStorage.getItem('userTheme');
    const theme = "dark"; // Simulate a retrieved value
    console.log("Retrieved user theme:", theme);
  } catch (error) {
    console.log("Error reading data:", error.message);
  }
}

main();

SQLite: Relational Database

For more complex data, like lists of items, user profiles with multiple fields, or anything requiring structured queries, SQLite is a powerful option.

It's a lightweight, embedded relational database that runs directly on the device. Think of it as a mini-serverless database.

When to Use SQLite

SQLite is ideal when you need:

Structured Data: Tables, columns, and relationships.
Complex Queries: Filtering, sorting, joining data.
Large Datasets: More efficient than key-value for many items.
Offline Sync: Storing data that will eventually sync with a backend.

However, it adds more complexity to your app's architecture.

Quick Check: Data Storage

Which local data storage method is generally best suited for storing a user's preference for 'dark mode' in a cross-platform mobile app?

Recap: Local Data Persistence

You've learned about essential local data persistence techniques for mobile apps!

Key-Value Stores: Simple for small data (Shared Preferences/UserDefaults, AsyncStorage).
AsyncStorage: Cross-platform (React Native) key-value, asynchronous.
SQLite: Embedded relational database for structured, complex data.

Choosing the right method depends on your data's complexity and your app's specific needs. Next, we'll explore integrating with remote APIs!

Frequently asked questions

Is the “Local Data Persistence” lesson free?

Yes — the full text of “Local Data Persistence” is free to read here on the web, and the Indie Hacker Mobile Apps course includes 4 lessons in total. To practise it interactively (a built-in code editor and a 24/7 AI tutor) and unlock the rest of the Indie Hacker Mobile Apps course, upgrade to CoddyKit PRO.

What will I learn in “Local Data Persistence”?

Learn various methods for storing and managing data locally on mobile devices, including SQLite, AsyncStorage, and shared preferences. You practise Indie Hacker Mobile Apps with hands-on code you run directly in the browser, and a 24/7 AI tutor answers your questions as you work through the lesson.

Do I need any experience to start Indie Hacker Mobile Apps?

No prior experience is required. Indie Hacker Mobile Apps on CoddyKit is structured for beginners through advanced learners; this is — lesson 2 of 4, so you can start here or from the beginning and move at your own pace.

How long does the “Local Data Persistence” lesson take?

Most CoddyKit lessons take about 5–10 minutes. Each one is bite-sized and interactive, so you make steady progress and pick up exactly where you left off across the web and the app.

Can I write and run code in this Indie Hacker Mobile Apps lesson?

Yes. Every Indie Hacker Mobile Apps lesson includes a built-in code editor, so you write and run real code right in your browser and get instant AI feedback — no local setup required.

All lessons in this course

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