Keep cold start under a set budget

How to do it

Google Play counts a cold start of 5 seconds or more as excessive. iOS ends an app that takes too long to launch. Do as little as possible before the first screen. Start SDKs late, load data after the first frame and avoid network calls on the launch path. Measure with a benchmark tool, such as Macrobenchmark on Android and XCTApplicationLaunchMetric on iOS. Run it on the same device model every time, and compare against the last release. The web counterpart is fail the build when pages get heavier.

Examples

Kotlin example

@Test
fun coldStartup() = benchmarkRule.measureRepeated(
    packageName = "com.example.fittrack",
    metrics = listOf(StartupTimingMetric()),
    iterations = 5,
    startupMode = StartupMode.COLD,
) {
    pressHome()
    startActivityAndWait()
}

Plain text example

func testColdStart() {
    measure(metrics: [XCTApplicationLaunchMetric()]) {
        XCUIApplication().launch()
    }
}

How to check

The CI startup benchmark runs 5 cold starts on the reference device. Their median stays within the budget and within 10% of the last release.

Sources

• Apple, Reducing your app's launch time
• Apple, XCTApplicationLaunchMetric
• Android vitals, App startup time

Related rules

• Fail the build when pages get heavier in Website