IntermediateBehavioral
Tell me about a time you significantly improved the performance of a user-facing page in a production frontend application.
Frontend Developer
General

Sample Answer

(S) On our main product dashboard, users complained about slow load times; initial load was ~6–7 seconds on 3G and our bounce rate was around 40%. (T) My task was to improve perceived and actual performance without a full rewrite. (A) I first profiled the app using Chrome DevTools and Lighthouse, identifying large bundle size (1.2 MB) and render-blocking scripts as key issues. I implemented code-splitting with dynamic imports for rarely used views, replaced a heavy charting library with a lighter alternative, and introduced image lazy-loading. I also optimized our webpack config with tree-shaking and vendor chunking. On the UX side, I added skeleton loaders for key panels so the page felt interactive sooner. (R) After deployment, the Time to Interactive dropped from ~6s to 2.8s on 3G, bundle size decreased by ~45%, and the dashboard’s bounce rate dropped from 40% to 24% over a month. Support tickets about slowness related to that page decreased by roughly 60%.

Keywords

Performance profiling with concrete toolsSpecific optimizations (code-splitting, lazy-loading, bundling)Use of metrics (TTI, bundle size, bounce rate)Clear STAR structureImpact on user experience and business metrics
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