In this lesson, you will learn how to choose between building your mobile app locally on your machine or utilizing cloud-based infrastructure to optimize your development workflow.
The Local Build Strategy
When you run npx expo run:ios or npx expo run:android, you are performing a local build. Your computer acts as the engine, utilizing your processor, RAM, and disk space to compile native code, link libraries, and package your assets.
- Pros: It is free, happens instantly without waiting in a queue, and allows for rapid iteration when you are tweaking native code or writing
config plugins. - Cons: It requires a beefy machine (especially for iOS builds, which require macOS). If your project becomes large, a local build can hog your system resources, making your computer sluggish for other tasks.
The Cloud Build Strategy (EAS Build)
Cloud build services, like EAS Build, offload the entire compilation process to remote servers. Instead of building on your laptop, you send your source code to a cloud environment configured specifically for mobile SDKs.
- Pros: It keeps your local machine fast, eliminates the need for maintaining complex native toolchains (like Xcode or Android Studio updates) locally, and provides consistent results across team members.
- Cons: You may encounter "queue times" where you wait for a server to become available, and there are often monthly costs or tier limits associated with these services.
How to Choose
The decision comes down to your current goal:
- Use Local Builds during the "Inner Loop" of development. If you are modifying your
app.jsonor fixing a UI bug, local builds provide the fastest feedback. You want to see changes on your simulator or device immediately. - Use Cloud Builds for the "Outer Loop." When you need to create a production-ready
.ipaor.apkfile for testing or store submission, the cloud is superior. It ensures your build is reproducible and handles complex tasks like code signing and environment-specific configuration automatically.
# Local development workflow
npx expo run:ios --device
# Cloud production workflow
eas build --platform ios
Key Takeaway: Build locally to iterate quickly on your code; use the cloud to handle the heavy lifting of production releases and ensure your build environment remains consistent.