Performance

Problems

• no boot
• slow (cold/warm/hot) start
• crash
• freeze/lock
• hanging
• slow/delay resp (ui, rtt)
• stutter (fps)
• error (un)handled (fe, be)
• tearing (ui:fps/hz, data)
• broken ui
• high battery (cpu)
• high/leaky ram
• fat bundle/app

Causes

• js
  • logic/renders, caching, nested views, ScrollView
  • native libs (reanimated/nav/flashlist/etc), state man arch, react 19 (compiler/useSyncExternalStore/etc)
• js engine
  • (webkit/android)jsc/v8/(static)hermes
• rn arch
  • old 60ps
  • new(jsi) 120fps
• renderer
  • fabric/skia
• modules
  • (turbo/nitro)modules
• starvation
  • 5% power saver mode (cpu)
  • 99% used (disk)
  • offline / 3G (network)
• user agent
  • blue light filter
  • magnification
• concurrency (threads)
  • hogging
  • (dead/live)lock
  • race condition
• backend
  • http/rest
  • gql
  • sockets
  • webrtc

Metrics

• release
  • adoption
  • crash-free sessions
  • new/retained/resurrected/inactive users
  • reviews/rating
• tti
  • tfcp
  • tfmp
• errors
  • (un)handled
  • stacktrace (sourcemaps)
  • events (analytics)
• ui
  • fps (js/native)
  • renders
• cpu
• ram
• network
  • rtt
  • downtime
• battery
• size
  • apk/ipa
  • js bundle (txt)
  • hbc (bin)
• analytics
  • events (single, series)
  • users (data, groups)
• e2e screens/vids
• The only metric that matters to me

Tools

Dev mode (errors/warnings)

• Flipper React Native DevTools
  • Perf Monitor

Release builds (perf)

• iOS: Xcode > Instruments
  • xcrun instruments xctrace
• Android: Studio Profiler
  • Systrace Perfetto

Libs

• 15Mar: Chrome DevTools (Remote JS Debugging)
• 16Apr: infinitered/reactotron
• 18Oct: rnfirebase>perf 💵
• 18Dec: welldone-software/why-did-you-render
• 20Feb: facebook/flipper
• 21Feb: oblador/react-native-performance
• 21Mar: getsentry/sentry-react-native 💵
• 21Mar: DataDog/dd-sdk-reactnative 💵
• 22Jun: Shopify/react-native-performance
• 22Jul: callstack/reassure
• 22Sep: bamlab/android-performance-profiler flashlight
• 23Aug: newrelic/newrelic-react-native-agent 💵
• 23May: Expo dev menu
• 24May: expo/atlas
• 24Oct: Expo dev tools (menu) plugins
• 24Oct: React Native DevTools (docs, Issues and Feedback)
  • @react-native/debugger-frontend (facebook/react-native-devtools-frontend)
    • @react-native/dev-middleware
  • react-native/ReactCommon/jsinspector-modern
• 24Dec: software-mansion/radon-ide

https://reactnative.dev/docs/next/performance

https://react.dev/reference/dev-tools/react-performance-tracks

No Problem