Frontend Interview Questions & Answers

Start by identifying what caused the bloat using bundle analysis tools (like `webpack-bundle-analyzer` or Vite bundle visualizer). Look for newly added heavy third-party libraries (e.g., Lodash whole package instead of cherry-picked methods, Moment.js instead of Day.js), unoptimized assets, or missing code-splitting. Then, implement dynamic imports (`import()`), route-based lazy loading, and tree-shaking.

Reproducing low-percentage bugs requires gathering robust telemetry and error-tracking data (using tools like Sentry, LogRocket, or Datadog). Look for common patterns among that 1%—such as specific device types, OS versions, browser extensions, viewport sizes, or localized language settings (like RTL layouts). Emulate these exact environments using browser developer tools or cloud testing device farms.

To handle high-frequency events (like window resizing, scrolling, or WebSocket data streams), use throttling or debouncing to limit execution frequency. Additionally, offload heavy data processing to Web Workers so the main UI thread remains unblocked and smooth for animations and user interactions.

Browser HTTP Caching: Best for static assets with content hashes (`Cache-Control: max-age=31536000, immutable`). CDN (Edge): Caches HTML, public pages, and static files close to the user globally to reduce origin server load. Service Worker: Enables offline experiences, precaching shell assets, and runtime caching of dynamic application data using strategies like Stale-While-Revalidate. API Layer / Database Caching: Handles server-side caching (e.g., Redis) for expensive database queries or computed responses.

Use Server Actions (popular in frameworks like Next.js) when performing direct form submissions or mutations tied closely to Server Components, as they reduce client-side boilerplate, eliminate manual endpoint creation, and seamlessly handle progressive enhancement. Use traditional API routes when building public-facing APIs consumed by external clients, mobile apps, or decoupled services.