android-performance-skill

name

android-performance-skill

description

Expert-level Android performance optimization skill. Use this skill whenever the user asks about anything related to Android app performance — including but not limited to: ANRs (Application Not Responding errors), crashes (NullPointerException, OOM, fatal exceptions), app startup time (cold start, warm start, hot start), UI jank or frame drops, memory leaks, battery drain, slow network calls, database/SQLite performance, overdraw, ProGuard/R8, Doze mode, WorkManager, RecyclerView performance, Bitmap/image loading, threading/coroutines, profiling with Android Studio, Perfetto, or Systrace. Trigger even if the user just mentions "my app is slow", "users are complaining about crashes", "ANR in Play Console", "startup is taking too long", or any vague performance complaint in an Android context. Always use this skill before answering Android performance questions — never rely on general memory alone.

Android Performance Optimization Skill

Quick Domain Index

Load the relevant reference file(s) based on the user's query. Multiple may apply.

Topic	Reference File	Keywords
ANRs	references/anr.md	ANR, Application Not Responding, main thread, blocked, 5 seconds, input dispatch
Crashes	references/crashes.md	crash, exception, OOM, NullPointer, fatal, Play Console vitals
App Startup	references/startup.md	cold start, warm start, hot start, TTID, TTFD, splash screen, AppStartup
UI & Rendering	references/ui-rendering.md	jank, frame drop, overdraw, RecyclerView, Choreographer, 16ms, 60fps, 90fps
Memory	references/memory.md	memory leak, OOM, heap, GC, LeakCanary, Bitmap, LargeHeap
Threading & Coroutines	references/threading.md	coroutines, threads, Dispatchers, StrictMode, main thread, background work
Network & Data	references/network.md	network, HTTP, OkHttp, Retrofit, caching, Gzip, payload size
Battery & Background	references/battery.md	battery, Doze, WorkManager, AlarmManager, wakelock, background
Database & Storage	references/database.md	Room, SQLite, query, index, SharedPreferences, DataStore
Build & Code Size	references/build-size.md	ProGuard, R8, APK size, app bundle, baseline profiles, dexopt
Profiling Tools	references/profiling.md	Android Studio Profiler, Perfetto, Systrace, Macrobenchmark, Microbenchmark, Tracing

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Response Philosophy

1. Diagnose first — Ask for or infer: device API level, whether it's debug/release, reproduction steps, any stack traces or Play Console data. Don't prescribe fixes before understanding root cause.
2. Show, don't just tell — Always include concrete Kotlin/Java code examples, not just advice.
3. Layered recommendations — Start with the highest-impact, easiest fix. Then go deeper.
4. Measurability — Every recommendation should include how to measure before/after (tooling, metrics).
5. Trade-offs — Be honest about trade-offs (e.g., aggressive caching vs memory pressure).

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Universal Performance Principles (always applicable)

• Never block the main thread. The Main/UI thread must complete each frame in <16ms (60fps) or <11ms (90fps). Any I/O, computation, or IPC on it causes jank or ANRs.
• Measure before optimizing. Gut feelings are wrong. Profile first.
• Understand the Android lifecycle. Most performance bugs come from misusing Activity/Fragment/ViewModel lifecycles.
• Release builds behave differently. Always validate performance on a release build with minification enabled.
• Real devices matter. Emulators don't replicate thermal throttling, low-RAM behavior, or GPU differences.

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Common Entry Points & Triage

"My app has ANRs in Play Console"

→ Read references/anr.md
Key questions: What's the ANR type? (Input dispatch timeout / Service timeout / Broadcast timeout). Load the ANR traces from Play Console and look for the main thread stack.

"My app is crashing"

→ Read references/crashes.md
Key questions: Is it OOM, a NullPointer, or another exception? Is it reproducible? Is there a stack trace?

"Cold start is too slow"

→ Read references/startup.md
Key questions: What is the current TTID? Are you using Jetpack App Startup? Is Application.onCreate() doing heavy work?

"My UI is janky / laggy"

→ Read references/ui-rendering.md
Key questions: Is it in a list (RecyclerView)? Is it on scroll? Is GPU overdraw visible? What does the frame timeline in Android Studio show?

"My app uses too much memory / has leaks"

→ Read references/memory.md
Key questions: Is LeakCanary showing leaks? Is it OOM on low-RAM devices? Are you loading large Bitmaps?

"Battery drain complaints"

→ Read references/battery.md
Key questions: Is the app running background services? Using wakelocks? Frequent network polling?

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Baseline: Always Recommend These

Regardless of the specific issue, the following should always be in place:

// 1. StrictMode in debug builds - catches main thread violations early
if (BuildConfig.DEBUG) {
    StrictMode.setThreadPolicy(
        StrictMode.ThreadPolicy.Builder()
            .detectAll()
            .penaltyLog()
            .build()
    )
    StrictMode.setVmPolicy(
        StrictMode.VmPolicy.Builder()
            .detectLeakedSqlLiteObjects()
            .detectLeakedClosableObjects()
            .detectActivityLeaks()
            .penaltyLog()
            .build()
    )
}

// 2. Use Baseline Profiles (in release) for faster startup JIT/AOT
// See references/build-size.md

// 3. Use Android Vitals in Play Console for real-world data
// ANR rate, crash rate, slow start rate, slow frames

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Metrics Reference (know your targets)

Metric	Good	Needs Work	Tool to Measure
Cold start TTID	< 1s	> 2s	Logcat ActivityTaskManager, Macrobenchmark
Warm start TTID	< 500ms	> 1.5s	Macrobenchmark
Hot start	< 200ms	> 500ms	Macrobenchmark
Frame render time	< 16ms	> 16ms (jank)	Android Studio Profiler, Perfetto
ANR rate	< 0.47%	> 1% (bad rating)	Play Console
Crash rate	< 1.09%	> 2% (bad rating)	Play Console / Firebase Crashlytics
Memory (mid-range)	< 200MB	> 300MB	Android Studio Memory Profiler
APK / AAB size	< 10MB	> 50MB (w/o reason)	Bundletool, Play Console