Code Splitting

Media queries are a CSS feature that allows you to apply styles conditionally based on device characteristics like viewport width, height, orientation, color scheme preference, or reduced motion settings. They are the backbone of responsive web design, enabling different layouts for mobile, tablet, and desktop screens. Modern media queries also support user preference detection with `prefers-color-scheme` and `prefers-reduced-motion` for more accessible experiences.

Flutter is Google's open-source UI toolkit for building natively compiled applications for mobile, web, and desktop from a single Dart codebase. Unlike React Native which maps to platform-native UI components, Flutter renders everything with its own high-performance Skia/Impeller rendering engine, giving developers pixel-perfect control over every element on screen. This approach ensures identical visual output across platforms but means Flutter widgets don't automatically adopt platform-specific design conventions.

Expo is a platform and set of tools built around React Native that simplifies mobile app development by providing a managed workflow, pre-configured native modules, and over-the-air update capabilities. With Expo, you can start building without installing Xcode or Android Studio, test on physical devices via the Expo Go app, and deploy updates without app store review cycles. Expo's EAS (Expo Application Services) handles cloud builds, submissions, and updates for production apps.

Static Site Generation (SSG) is a rendering strategy where HTML pages are pre-built at build time rather than generated on each request. The resulting static files can be served from a CDN with extremely fast load times and minimal server infrastructure. Frameworks like Next.js, Gatsby, and Astro support SSG, often combined with Incremental Static Regeneration (ISR) to update specific pages in the background without rebuilding the entire site.

Blue-green deployment is a release strategy that maintains two identical production environments — "blue" (current) and "green" (new version). Traffic is switched from blue to green only after the new version passes all health checks, enabling zero-downtime releases. If issues are detected, traffic can be instantly routed back to the blue environment, making rollbacks trivial and fully automated.

Reconciliation is React's algorithm for comparing the previous and current Virtual DOM trees to determine the minimum number of changes needed to update the actual DOM. React uses heuristics like element type comparison and the `key` prop to efficiently decide whether to update, replace, or remove DOM nodes. Understanding reconciliation explains why unique `key` props on list items matter — without them, React can't reliably track which items changed, leading to bugs and poor performance.