How do you reduce app startup time?

Startup has native and JavaScript phases. The OS launches the process and native app delegate, then the JS runtime loads the bundle, evaluates modules and renders the first screen. Optimising the wrong phase wastes effort, so measure from process start to first meaningful paint.

Where time goes

• Native initialisation and third-party SDK setup
• Bundle download or read, parsing and module evaluation
• Synchronous storage reads and token refresh before the first screen
• Rendering a heavy initial screen with too many views
• Analytics and feature-flag SDKs blocking the main thread

import { InteractionManager } from "react-native";

export function deferUntilIdle(task: () => void) {
  const handle = InteractionManager.runAfterInteractions(task);
  return () => handle.cancel();
}

Use Hermes so the bundle ships as bytecode and starts faster than parsing plain JavaScript. Keep the initial route small, lazy-load heavy screens and SDKs, and avoid importing large modules at the top of the entry file. Inline requires can help, but verify the effect on your bundle rather than assuming.