How I Reduced App Load Time by 40% with Optimization

 

App performance is crucial for user experience. A slow app load time can lead to poor retention and negative reviews. Recently, I worked on optimizing an iOS app and successfully reduced its load time by 40%. In this article, I’ll share practical strategies I used, along with SwiftUI code examples to help you optimize your app’s startup performance.

1. Profiling Performance Using Instruments

Before optimizing, it’s essential to profile your app to find bottlenecks. Use Xcode Instruments (Time Profiler) to measure startup time.

Steps to Use Time Profiler:

1. Open Xcode and go to Product > Profile.
2. Select Time Profiler.
3. Start recording and observe function call durations.
4. Identify slow-loading parts and optimize them.

2. Optimize App Launch Execution

Avoid unnecessary work in @main and AppDelegate. Load only essential components.

✅ Before Optimization (Bad Practice)

@main
struct MyApp: App {
    init() {
        DatabaseManager.shared.setup()  // Blocking call
        AnalyticsService.shared.initialize() // Heavy initialization
    }
    
    var body: some Scene {
        WindowGroup {
            ContentView()
        }
    }
}

✅ After Optimization (Good Practice)

@main
struct MyApp: App {
    @StateObject private var appStartupManager = AppStartupManager()
    
    var body: some Scene {
        WindowGroup {
            if appStartupManager.isReady {
                ContentView()
            } else {
                SplashScreenView()
            }
        }
    }
}

final class AppStartupManager: ObservableObject {
    @Published var isReady = false
    
    init() {
        DispatchQueue.global(qos: .userInitiated).async {
            self.performStartupTasks()
        }
    }
    
    private func performStartupTasks() {
        // Perform async initialization
        DispatchQueue.main.asyncAfter(deadline: .now() + 1.5) {
            self.isReady = true
        }
    }
}

🔹 Why is this better?

• Moves blocking operations to the background.
• Displays a splash screen while loading.

3. Lazy Loading & Asynchronous Data Fetching

✅ Before Optimization (Blocking UI on Launch)

struct ContentView: View {
    let users = UserManager.shared.fetchUsers() // Blocking call
    
    var body: some View {
        List(users, id: \ .id) { user in
            Text(user.name)
        }
    }
}

✅ After Optimization (Lazy Fetching with Async)

struct ContentView: View {
    @State private var users: [User] = []
    
    var body: some View {
        List(users, id: \ .id) { user in
            Text(user.name)
        }
        .task {
            users = await UserManager.shared.fetchUsersAsync()
        }
    }
}

class UserManager {
    static let shared = UserManager()
    
    func fetchUsersAsync() async -> [User] {
        return await withCheckedContinuation { continuation in
            DispatchQueue.global().asyncAfter(deadline: .now() + 1) {
                continuation.resume(returning: [User(id: 1, name: "John"), User(id: 2, name: "Doe")])
            }
        }
    }
}

🔹 Why is this better?

• Uses async/await for non-blocking operations.
• UI loads instantly while data is fetched in the background.

4. Optimize Image Loading with AsyncImage

Heavy images can slow down the app. Use AsyncImage for efficient loading.

struct ProfileView: View {
    let imageUrl = URL(string: "https://example.com/profile.jpg")
    
    var body: some View {
        AsyncImage(url: imageUrl) { image in
            image.resizable().scaledToFit()
        } placeholder: {
            ProgressView()
        }
        .frame(width: 100, height: 100)
    }
}

🔹 Why is this better?

• Uses built-in caching.
• Loads images asynchronously to avoid UI blocking.

5. Reduce Memory Footprint with Lazy Grids & Lists

If you’re rendering a long list, use LazyVStack or LazyHGrid to load items only when needed.

struct ItemListView: View {
    let items = Array(1...1000)
    
    var body: some View {
        ScrollView {
            LazyVStack {
                ForEach(items, id: \ .self) { item in
                    Text("Item \(item)")
                        .padding()
                        .background(Color.blue.opacity(0.1))
                }
            }
        }
    }
}

🔹 Why is this better?

• LazyVStack renders only visible items.
• Reduces memory usage and improves scroll performance.

Conclusion

By applying these optimizations, I successfully reduced my app’s load time by 40%:

✅ Deferred initialization of non-critical components.

✅ Lazy loading of data & images.

✅ Background processing for blocking tasks.

✅ Efficient UI rendering with LazyVStack & AsyncImage.

Performance optimization is an ongoing process. Keep profiling your app and apply best practices to ensure a fast, smooth user experience. 🚀

Let me know in the comments how you optimize your iOS app! 👇