Blue-Green Deployment

Shadow DOM is a browser API that allows you to attach a hidden, encapsulated DOM tree to an element, isolating its styles and markup from the rest of the page. This means CSS defined inside a Shadow DOM won't leak out, and external styles won't bleed in. It's the core technology behind Web Components and is used by frameworks to achieve true style encapsulation without CSS naming conventions or tooling.

Memoization in React is a performance optimization that caches the result of expensive computations or component renders to avoid redundant work on re-renders. React provides `React.memo()` to skip re-rendering a component when its props haven't changed, `useMemo()` to cache computed values, and `useCallback()` to cache function references. While powerful, premature memoization adds complexity — it's best applied after profiling confirms an actual performance bottleneck.

Hot reload is a development feature that injects updated code into a running application without restarting it or losing the current state. In Flutter, hot reload works by injecting updated Dart source code into the running Dart VM, typically completing in under a second. React Native offers a similar feature called Fast Refresh that preserves component state during edits. Both dramatically accelerate the development feedback loop compared to traditional compile-and-restart cycles.

Lazy loading is a performance optimization technique that defers loading of non-critical resources until they are actually needed — typically when they enter the viewport. It is commonly applied to images, videos, and below-the-fold components to speed up initial page load. Modern browsers support native lazy loading via the `loading="lazy"` attribute, while JavaScript-based solutions offer more control through Intersection Observer.

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.

CI/CD (Continuous Integration / Continuous Deployment) is a set of practices that automate building, testing, and deploying code every time a developer pushes changes. Continuous Integration merges code into a shared branch frequently and runs automated tests, while Continuous Deployment automatically releases validated changes to production. Together they form the backbone of modern software delivery, reducing manual errors and accelerating release cycles.