React Native & Expo

React Native exists synonymously with a technology called Expo. Expo is essentially a toolkit of useful libraries and tools for React Native, backed by a company that also provides infrastructure called EAS (Expo Application Services).

Why Expo?

It’s not particularly appealing to vendor-lock yourself. But when it comes to React Native, Expo is an absolute no-brainer, and using Expo does not make you beholden to EAS.

One key benefit is the development environment, which ties perfectly into Mosayic’s local-first philosophy. Unlike the hassles of web-based development environments (like FlutterFlow’s test mode), you can run Expo completely in your local development environment. Through the magic of your local Wi-Fi network, you can run your application build on your physical device – like your phone – as you’re coding it.

Tip

Even if you’re not developing on a Mac but want to build your app in real-time on an iPhone, Expo makes this possible.

Expo Application Services (EAS)

EAS is optional – you can use Expo without it – but Mosayic is built on the premise that you will use it. Push notifications, for example, are handled by EAS.

The company behind EAS makes their real money through builds. And while it’s true that uploading to the App Store and Play Store, getting code-signing right, and navigating platform-specific quirks is an absolute headache. But at the same time, we don’t want to have to spend more than we must on builds.

Note

While Mosayic integrates with EAS and sets it up for you, it also makes build costs more manageable by incorporating another tool, CodeMagic – which we’ll cover later.

Running the Development Server

Mosayic runs the Expo server and provides a QR code. Scan it to install and open the Expo Go app on your device. As you or your AI agent builds your React Native application, you can see changes in real-time on your physical device.

Building Your App

Mosayic is not opinionated about how you build the actual React Native codebase. It starts you with a template and some instructions – from there, how you build your mobile application is completely up to you.

This falls into the realm of:

• How good your coding agent is
• Latest trends in AI coding
• Whether you use context engineering
• Whether you follow the latest YouTube discourse on Cursor vs Claude Code vs Windsurf vs Codex vs Gemini

Note

Mosayic isn’t concerned with keeping pace with AI coding trends. It’s an architecture framework, focused on infrastructure rather than coding methodology.

However, Mosayic does bring attention to infrastructure-related aspects of your mobile application – like push notifications and database interaction. Your AI is absolutely capable of navigating these integrations once it has the context that the template provides.