Blogs on React, performance, and big-tech optimizations. Written from the middle of learning. By Ashish.https://renderlog.in/en-ushttps://renderlog.in/blog/json-parse-errors-debugging/https://renderlog.in/blog/json-parse-errors-debugging/What each JSON.parse() SyntaxError actually means, how to find the real cause fast, and when parsing large JSON becomes a main thread performance problem.Tue, 21 Apr 2026 00:00:00 GMTjavascriptdebuggingjsondeveloper-toolsperformanceAshishhttps://renderlog.in/blog/preact-vs-react-why-3kb-alternative-exists/https://renderlog.in/blog/preact-vs-react-why-3kb-alternative-exists/React's 45KB comes from synthetic events and compatibility layers Preact drops. At 3KB, it calls native DOM directly. Here is what that trade-off means.Tue, 21 Apr 2026 00:00:00 GMTperformancereactpreactjavascriptfrontendAshishhttps://renderlog.in/blog/service-worker-caching-strategies-workbox/https://renderlog.in/blog/service-worker-caching-strategies-workbox/The best network request never happens. Service workers intercept and serve from cache. Here are the three Workbox caching strategies and when to use each.Mon, 20 Apr 2026 00:00:00 GMTperformancejavascriptcachingbrowserworkboxAshishhttps://renderlog.in/blog/preload-prefetch-preconnect-resource-hints-guide/https://renderlog.in/blog/preload-prefetch-preconnect-resource-hints-guide/Three resource hints, three different jobs. Using the wrong one wastes bandwidth and slows the current page. How each one works and when to apply it.Sun, 19 Apr 2026 00:00:00 GMTperformancebrowsernetworkLCPfrontendAshishhttps://renderlog.in/blog/critical-css-inlining-render-blocking-explained/https://renderlog.in/blog/critical-css-inlining-render-blocking-explained/The browser cannot paint until it builds the CSSOM. CSS in an external file means a round trip before the first pixel. Inlining critical CSS removes that.Sat, 18 Apr 2026 00:00:00 GMTperformancecssbrowserLCPrenderingAshishhttps://renderlog.in/blog/http2-multiplexing-frontend-performance-changes/https://renderlog.in/blog/http2-multiplexing-frontend-performance-changes/Domain sharding, CSS sprites, and JS concatenation were correct for HTTP/1.1. HTTP/2 turned them into anti-patterns. Here is what changed and why.Fri, 17 Apr 2026 00:00:00 GMTperformancenetworkbrowserjavascriptfrontendAshishhttps://renderlog.in/blog/react-lazy-route-code-splitting-guide/https://renderlog.in/blog/react-lazy-route-code-splitting-guide/React.lazy() makes a 5MB app's first load equal to just the landing route cost. Here is how route code splitting works and where it silently fails.Wed, 15 Apr 2026 00:00:00 GMTperformancereactbundlingjavascriptcode-splittingAshishhttps://renderlog.in/blog/skeleton-screens-vs-spinners-perceived-performance/https://renderlog.in/blog/skeleton-screens-vs-spinners-perceived-performance/Perceived and measured performance diverge more than most developers expect. LinkedIn's skeleton screen research explains why, and when skeletons hurt.Tue, 14 Apr 2026 00:00:00 GMTperformancefrontenduxreactrenderingAshishhttps://renderlog.in/blog/srcset-sizes-responsive-images-explained/https://renderlog.in/blog/srcset-sizes-responsive-images-explained/The correct image for any device depends on viewport width, pixel density, and connection speed. srcset and sizes make that computable at the HTML level.Mon, 13 Apr 2026 00:00:00 GMTperformanceimagesbrowserfrontendLCPAshishhttps://renderlog.in/blog/loading-lazy-html-attribute-how-it-works/https://renderlog.in/blog/loading-lazy-html-attribute-how-it-works/Google's profiling found 30-50% of bandwidth goes to below-fold images. loading="lazy" defers them, but two cases where it actively hurts LCP.Sun, 12 Apr 2026 00:00:00 GMTperformanceimagesbrowserLCPfrontendAshishhttps://renderlog.in/blog/frontend-performance-how-why-hub/https://renderlog.in/blog/frontend-performance-how-why-hub/All blogs in the React & JS Performance series in reading order, plus quick reference on layout thrashing, will-change, passive listeners, and INP.Sat, 04 Apr 2026 00:00:00 GMTperformancejavascriptfrontendreactwebAshishhttps://renderlog.in/blog/frontend-performance-interview-approach/https://renderlog.in/blog/frontend-performance-interview-approach/How to answer practical frontend performance interviews in React: a seven-area framework—rendering, network, mobile, bundles, assets, memory, and measurement.Sat, 04 Apr 2026 00:00:00 GMTperformanceinterviewreactfrontendjavascriptAshishhttps://renderlog.in/blog/lighthouse-100-still-crashes-memory/https://renderlog.in/blog/lighthouse-100-still-crashes-memory/Why a perfect Lighthouse score doesn't prevent out-of-memory tab crashes in long-running SPAs — and how to build apps that survive 8-hour sessions.Sat, 04 Apr 2026 00:00:00 GMTperformancememorylighthousemobiledebuggingAshishhttps://renderlog.in/blog/build-bundles-treeshaking-code-splitting/https://renderlog.in/blog/build-bundles-treeshaking-code-splitting/Your 2MB bundle isn't fate. How bundlers merge modules, why tree shaking fails silently, and how to split code so users only load what they need.Fri, 03 Apr 2026 00:00:00 GMTperformancebundlingjavascriptcode-splittingfrontendAshishhttps://renderlog.in/blog/images-fonts-third-party-performance/https://renderlog.in/blog/images-fonts-third-party-performance/How image formats, font loading, and third-party tag managers silently destroy LCP and CLS scores, and the exact fixes for each that actually work.Fri, 03 Apr 2026 00:00:00 GMTperformanceimagesfontsLCPfrontendAshishhttps://renderlog.in/blog/javascript-garbage-collection-frontend/https://renderlog.in/blog/javascript-garbage-collection-frontend/How V8's generational garbage collector works, why high allocation rate causes jank, and practical strategies to reduce GC pressure in frontend code.Fri, 03 Apr 2026 00:00:00 GMTjavascriptperformancememoryv8frontendAshishhttps://renderlog.in/blog/react-memory-retained-graphs-leaks/https://renderlog.in/blog/react-memory-retained-graphs-leaks/How WebSocket subscriptions, stale closures, and unbounded caches create memory leaks in React apps — and how to find and fix them with Chrome DevTools.Fri, 03 Apr 2026 00:00:00 GMTreactperformancememoryleaksjavascriptAshishhttps://renderlog.in/blog/mobile-web-dom-performance/https://renderlog.in/blog/mobile-web-dom-performance/Budget Android devices run your JS 5-10x slower than your MacBook. Content-visibility, CSS containment, touch scroll, and real debugging on low-end hardware.Thu, 02 Apr 2026 00:00:00 GMTperformancemobileDOMcssfrontendAshishhttps://renderlog.in/blog/network-optimization-spa-react/https://renderlog.in/blog/network-optimization-spa-react/Why React SPAs refetch data you already have, and how to fix it: HTTP cache headers, stale-while-revalidate, request deduplication, and prefetch strategies.Thu, 02 Apr 2026 00:00:00 GMTperformancenetworkreactcachingfrontendAshishhttps://renderlog.in/blog/origin-private-file-system-opfs/https://renderlog.in/blog/origin-private-file-system-opfs/Origin Private File System gives browsers a real sandboxed filesystem. How it compares to IndexedDB, Cache API, and why it's the right tool for 200MB+ assets.Thu, 02 Apr 2026 00:00:00 GMTperformanceOPFSstorageweb-workersjavascriptAshishhttps://renderlog.in/blog/web-workers-frontend-react/https://renderlog.in/blog/web-workers-frontend-react/CPU-heavy tasks block the UI — Web Workers fix that. Integrate Workers in React with Comlink, custom hooks, and Vite, with before/after profiling results.Thu, 02 Apr 2026 00:00:00 GMTperformanceweb-workersjavascriptreactfrontendAshishhttps://renderlog.in/blog/large-lists-virtualization-trade-offs/https://renderlog.in/blog/large-lists-virtualization-trade-offs/10,000 DOM nodes is slow even if they're not visible. When to paginate, when to infinite scroll, when to virtualize — and the real cost of each approach.Wed, 01 Apr 2026 00:00:00 GMTperformancereactvirtualizationlistsfrontendAshishhttps://renderlog.in/blog/react-concurrent-features-performance/https://renderlog.in/blog/react-concurrent-features-performance/How startTransition and useDeferredValue fix frozen inputs and laggy UIs by separating urgent updates from deferred ones — with real before/after examples.Wed, 01 Apr 2026 00:00:00 GMTreactperformanceconcurrentstartTransitionfrontendAshishhttps://renderlog.in/blog/react-memo-usememo-usecallback/https://renderlog.in/blog/react-memo-usememo-usecallback/Most React memoization is premature. This breaks down when memo, useMemo, and useCallback actually help and when they add memory overhead with no real gain.Wed, 01 Apr 2026 00:00:00 GMTreactperformanceuseMemouseCallbackfrontendAshishhttps://renderlog.in/blog/react-rerendering-when-trees-update/https://renderlog.in/blog/react-rerendering-when-trees-update/Render phase vs commit phase, reconciliation and fibers, what triggers re-renders, referential equality traps, context pitfalls, and React 18 batching.Wed, 01 Apr 2026 00:00:00 GMTreactperformancerenderingreconciliationfrontendAshishhttps://renderlog.in/blog/aadhaar-deduplication-billion-scale/https://renderlog.in/blog/aadhaar-deduplication-billion-scale/How Aadhaar's ABIS deduplicates biometrics at billion scale: fingerprint templates, iris codes, sharded search, multi-engine consensus, and score fusion.Tue, 31 Mar 2026 00:00:00 GMTaadhaaridentityscaleengineeringinfrastructureAshishhttps://renderlog.in/blog/long-tasks-main-thread-blocking/https://renderlog.in/blog/long-tasks-main-thread-blocking/What >50ms Long Tasks are, why they destroy INP, and how to chunk work with scheduler.yield(), postTask(), and Web Workers to keep the UI responsive.Tue, 31 Mar 2026 00:00:00 GMTperformancejavascriptlong-tasksINPschedulingAshishhttps://renderlog.in/blog/lottie-airbnb-json-animation/https://renderlog.in/blog/lottie-airbnb-json-animation/How Lottie works: JSON After Effects timelines rendered by cross-platform runtimes. Why Airbnb chose vector JSON over GIF and video for UI animations.Tue, 31 Mar 2026 00:00:00 GMTlottieanimationfrontendmobiledesignAshishhttps://renderlog.in/blog/core-web-vitals-lighthouse-explained/https://renderlog.in/blog/core-web-vitals-lighthouse-explained/LCP, CLS, INP, and TTFB explained at the technical level. What lab scores miss about real users, how CrUX data differs, and what to fix when metrics look green.Mon, 30 Mar 2026 00:00:00 GMTperformancecore-web-vitalslighthouseLCPINPAshishhttps://renderlog.in/blog/drm-pip-loophole/https://renderlog.in/blog/drm-pip-loophole/Why Picture-in-Picture can bypass DRM black-screen protection in browsers: compositor paths, Widevine L3 vs L1 decode routing, and why 4K stays stubborn.Mon, 30 Mar 2026 00:00:00 GMTdrmwidevinestreamingweb-platformchromeAshishhttps://renderlog.in/blog/meta-stylex-compile-time-styling/https://renderlog.in/blog/meta-stylex-compile-time-styling/How Meta StyleX compiles JS-authored styles into atomic static CSS. No runtime injection, smaller bundles, and why the build-time approach matters at scale.Mon, 30 Mar 2026 00:00:00 GMTstylexcssfrontendjavascriptmetaAshishhttps://renderlog.in/blog/rapido-rapid-pin-static-otp/https://renderlog.in/blog/rapido-rapid-pin-static-otp/Rapido's fixed 4-digit Rapid PIN vs dynamic OTP: UX, SMS cost, and why physical pickup context matters more than brute-force odds.Mon, 30 Mar 2026 00:00:00 GMTuxproductsecurityengineeringmobilityAshishhttps://renderlog.in/blog/16ms-frame-budget-60fps/https://renderlog.in/blog/16ms-frame-budget-60fps/At 60Hz the browser has ~16.6ms per frame for JS, layout, and paint. Why load scores miss jank and what it means for trading and live data UIs.Sun, 29 Mar 2026 00:00:00 GMTperformancejavascriptfrontendrenderingreactAshishhttps://renderlog.in/blog/google-maps-traffic-live-prediction/https://renderlog.in/blog/google-maps-traffic-live-prediction/Live traffic in Google Maps: how probe data, graph routing, Waze-style reports, and historical speed curves combine to show jams and update ETAs at huge scale.Sun, 29 Mar 2026 00:00:00 GMTgoogle-mapstrafficgpsdata-engineeringmappingAshishhttps://renderlog.in/blog/react-state-management-patterns/https://renderlog.in/blog/react-state-management-patterns/Redux, Zustand, Jotai, and Valtio compared from the inside. Centralized, atomic, and proxy-based React state patterns and when each one wins on scale.Sun, 29 Mar 2026 00:00:00 GMTreactstate-managementjavascriptfrontendreduxAshishhttps://renderlog.in/blog/why-react-error-boundaries-class-components/https://renderlog.in/blog/why-react-error-boundaries-class-components/React error boundaries use class lifecycles, not hooks: what render errors they catch, what async and event errors they skip, and how to structure fallbacks.Sun, 29 Mar 2026 00:00:00 GMTreactjavascriptfrontenderror-handlingreact-hooksAshishhttps://renderlog.in/blog/browser-main-thread-rendering-pipeline/https://renderlog.in/blog/browser-main-thread-rendering-pipeline/Parse → DOM → CSSOM → Layout → Paint → Composite. What the main thread does each frame, what jank physically is, and how to stop causing it.Sat, 28 Mar 2026 00:00:00 GMTperformancebrowserrenderingjavascriptfrontendAshishhttps://renderlog.in/blog/drm-screen-capture-jiohotstar/https://renderlog.in/blog/drm-screen-capture-jiohotstar/Why streaming apps go black on screen capture: EME, CDMs, Widevine L1 vs L3, and the secure compositor paths that keep decrypted frames off the capture surface.Sat, 28 Mar 2026 00:00:00 GMTdrmstreamingweb-platformsecuritywidevineAshishhttps://renderlog.in/blog/why-css-never-matches-figma/https://renderlog.in/blog/why-css-never-matches-figma/Browsers share one CSS model; Figma uses WASM and GPU shaders. Where design-to-code breaks: radius, strokes, blur, gap, and what to verify before you build.Sat, 28 Mar 2026 00:00:00 GMTfigmacssdesign-handofffrontendweb-platformAshish