Frontend Performance Optimization Questions

Comprehensive techniques and trade offs for improving client side performance in web applications and single page applications. Candidates should understand the browser rendering pipeline and critical rendering path including parsing, style calculation, layout, paint, and compositing, and how layout and paint costs produce reflow and repaint. They should know how component design and code patterns affect rendering and how to avoid layout thrashing and unnecessary re rendering. Candidates must be able to diagnose and mitigate JavaScript execution bottlenecks and long tasks that block the main thread using browser developer tools and performance application programming interfaces. Key topics include bundling and module strategies such as code splitting, lazy loading, tree shaking, and bundle size reduction; image optimization and responsive image techniques; network optimization including resource prioritization, compression, and caching strategies; service workers for offline capabilities and advanced caching patterns; and use of web workers to offload computation. Advanced considerations include virtual scrolling for large lists, progressive enhancement, server side rendering and client side rendering trade offs and hydration cost for universal applications, browser memory management and garbage collection implications, and how frontend decisions interact with backend constraints and overall system architecture. Candidates should also be familiar with measuring user experience using Core Web Vitals such as Largest Contentful Paint, First Input Delay, and Cumulative Layout Shift, with real user monitoring and synthetic testing, and with establishing performance budgets and continuous performance monitoring.