Example Concept: To optimize app startup time, focus on reducing the initial workload by deferring non-critical operations until after the app is fully launched. This can be achieved by lazy loading resources, using lightweight initial views, and optimizing the main thread workload. On iOS, consider using SwiftUI's efficient rendering and on Android, leverage Jetpack Compose's composable functions to streamline UI rendering. Both platforms benefit from profiling tools like Xcode Instruments and Android Profiler to identify bottlenecks.