Img Src: chatGPT

When you tap on WhatsApp, Netflix, or Zomato, the first few seconds decide whether you’ll stay or churn. As users, we expect apps to just work instantly. As architects, we know those seconds hide a complex chain of initializations, dependency graphs, caching, and remote configs.

That invisible orchestration is called App Startup.

What is App Startup?

App startup is the process from the moment an app is launched to when it becomes interactive. It includes:

1. Process Initialization — OS creates the app process (Android Zygote fork, iOS binary load).
2. Framework Bootstrapping — Application runtime and UI toolkit initialization.
3. Dependency Setup — Logging, crash reporting, DI containers, networking clients.
4. Configuration & Authentication — Remote configs, feature flags, token validation.
5. UI Rendering (First Draw) — First frame (splash, skeleton screen) is painted.
6. Data Hydration — Cached data shown instantly, server sync in background.

Types of Startup

• Cold Start: From scratch (e.g., Paytm after device reboot).
• Warm Start: Process exists but not visible (switching back to Zomato).
• Hot Start: Instant resume from background (Instagram reopen).

👉 Research shows if an app takes more than 3 seconds to start, retention drops significantly. For product-based companies, this translates to lost orders, failed conversions, or frustrated users.

 

What is App Startup?

App startup refers to the process from launching an app to when it becomes interactive. It includes several stages that ensure the app is ready to be used smoothly:

1. Process Initialization
   The operating system (OS) creates the app’s process, such as Android forking the Zygote process or iOS loading the app binary.
2. Framework Bootstrapping
   This is the OS-level setup before the app’s code runs, including initializing core components like the Android Runtime (ART), class loaders, and UI toolkit.
3. Dependency Setup
   This stage includes setting up services like logging, crash reporting, networking clients, and dependency injection (DI) containers.
4. Configuration & Authentication
   At this point, remote configurations are fetched, feature flags are evaluated, and authentication tokens are validated.
5. UI Rendering (First Draw)
   The first screen is rendered, often with a splash screen or skeleton UI while the app continues to load content in the background.
6. Data Hydration
   Cached data is displayed instantly, and additional data is fetched or synchronized from the server in the background.

 

Types of Startup

• Cold Start — This occurs when the app is launched from scratch, such as when the device is rebooted or the app is force-closed. (e.g., Paytm)
• Warm Start — This happens when the app process is still running but not visible. For example, switching back to an app like Zomato.
• Hot Start- In this case, the app resumes instantly from the background, like reopening Instagram.

 

Why App Startup Speed Matters

Research shows that if an app takes more than 3 seconds to start, user retention drops significantly. This leads to:

• Lost orders
• Failed conversions
• Frustrated users

For product-based companies, a slow app startup can directly impact revenue and user satisfaction.

The Two Layers of App Startup

1. System-Level Bootstrapping (Handled by the OS)

The OS handles the initial setup of the app, including:

• Zygote Process Forking: Android creates a process (zygote) that already has core classes in memory.
• Runtime Setup: Android initializes the ART (Android Runtime), class loaders, and the app’s main thread.
• UI Toolkit Initialization: Prepares the UI system for rendering, including components like Skia, SurfaceFlinger, and the input pipeline.
• App Process Launch: The OS then calls the app’s Application class to kick off the app’s logic.

Note: Developers don’t control this part; it’s all managed by the operating system, much like starting a car engine (ignition, fuel, cylinders firing).

2. App-Level Initialization (Handled by the Developer)

Once the system initializes the app’s process, the app itself begins its startup sequence:

• Traditionally, everything would be crammed into the Application.onCreate() method, causing slow cold starts, UI jank, and maintenance headaches.
• Jetpack App Startup (for Android) improves this by providing a declarative API for initializing libraries and components, allowing developers to better manage dependencies and lazy-load heavy components.

How Jetpack App Startup Works:

1. System Bootstraps the App
   The OS does the initial setup.
2. AppInitializer Discovers Components
   The AppInitializer discovers the app’s dependencies by reading the app’s manifest file.
3. Initializers Run in Dependency Order
   Each component is initialized in the order of its dependencies, ensuring everything is set up correctly.
4. Lazy Initialization for Non-Critical Components
   Non-essential components, like analytics or push notifications, are lazy-loaded to improve startup performance.

Real-World Examples

• WhatsApp: Prioritizes quick messaging by eagerly loading logging and database components, while analytics and push notifications are lazy-loaded in the background.
• Netflix: The “N” splash animation hides the time-consuming DRM checks and configuration fetches.
• Zomato/Swiggy: Cached restaurant lists are shown immediately, while server synchronization happens in the background.
• Paytm/PhonePe: Crashlytics, logging, and security SDKs initialize early, but payment SDKs are lazy-loaded just when needed, such as during a transaction.

Android Jetpack App Startup Example

class CrashlyticsInitializer : Initializer<Crashlytics> {
override fun create(context: Context): Crashlytics {
return Firebase.crashlytics
}
override fun dependencies() = emptyList<Class<out Initializer<*>>>()
}

class AnalyticsInitializer : Initializer<Analytics> {
override fun create(context: Context): Analytics {
return Analytics(context).apply { initialize() }
}
override fun dependencies() = listOf(CrashlyticsInitializer::class.java)
}

 

Key points:

• Analytics depends on Crashlytics → DAG ensures correct order.
• Heavy operations should be deferred.
• App Startup library replaces the old “multiple ContentProvider per SDK” pattern, reducing startup cost.

 

Startup Flow Diagram

 

Best Practices

1. Keep Initializers Lean — Only synchronous essential work in create().
2. Lazy & Deferred Init — Heavy SDKs (ads, ML models) should be deferred.
3. Bake Defaults — Ship cached configs; fetch updates asynchronously.
4. Measure Continuously — Track time-to-first-draw, time-to-interactive.
5. Perception Matters — Skeleton UIs, cached data, preloading tricks improve UX.

Common Pitfalls

• Over-initialization → kills cold start.
• Blocking network calls → delays first screen.
• Circular dependencies → crashes.
• No observability → regressions unnoticed.

Conclusion
App startup is where engineering meets business outcomes.

• WhatsApp → instant → trust.
• Netflix → smooth → delight.
• Zomato → responsive → conversion.

On Android, Jetpack App Startup enables structured, fast, and safe initialization with dependency-aware initializers.

Remember: the user doesn’t care about DAGs or SDKs — they only care that the app is ready the moment they tap it.

Thanks for reading! If you found this article helpful and want to stay in touch, feel free to connect with me on LinkedIn. I’m always open to discussing tech trends, career advice, or just networking with like-minded professionals. Let’s grow together in this ever-evolving tech landscape!

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This article was previously published on proandroiddev.com