Context API

Tree shaking is a dead code elimination technique used by modern bundlers like Webpack, Rollup, and esbuild to remove unused exports from the final JavaScript bundle. It relies on the static structure of ES module `import`/`export` syntax to determine which code is actually referenced and safely discard the rest. For tree shaking to work effectively, libraries must use ESM format and avoid side effects in their module initialization, which is why the `sideEffects` field in `package.json` matters.

Idempotency means that performing the same operation multiple times produces the same result as performing it once. This property is critical in automation and distributed systems where network failures or retries may cause a request to be sent more than once. APIs, payment processing, and deployment scripts should be designed to be idempotent so that retries are safe and don't create duplicate side effects.

CSS Modules are CSS files where all class names are locally scoped by default, meaning they're automatically transformed into unique identifiers at build time to prevent naming collisions. You import them into your JavaScript as an object and reference classes like `styles.button` instead of plain strings. This approach is natively supported by bundlers like Webpack, Vite, and Next.js, offering style isolation without the runtime overhead of CSS-in-JS.

A cron job is a time-based task scheduler originating from Unix systems that runs commands or scripts at specified intervals. The schedule is defined using a cron expression with five fields representing minute, hour, day, month, and weekday. Cron jobs are fundamental for automations like database backups, log rotation, report generation, and periodic data synchronization.

React Hooks are functions (like `useState`, `useEffect`, `useMemo`, `useCallback`) that let you use state, side effects, and other React features inside functional components without writing classes. Introduced in React 16.8, they fundamentally changed how React applications are structured by enabling logic reuse through custom hooks. Hooks must follow two rules: they can only be called at the top level of a component, and only inside React function components or other hooks.

Dart is the programming language created by Google and used as the sole language for Flutter development. It features a sound type system, null safety, async/await support, and compiles both ahead-of-time (AOT) for production performance and just-in-time (JIT) for fast development cycles with hot reload. Dart's syntax feels familiar to developers coming from JavaScript, TypeScript, Java, or Kotlin, making the transition to Flutter relatively smooth.