Monitoring App Performance on iOS
Article Summary
Expedia's iOS team breaks down the complete performance monitoring toolkit every mobile team needs. Your users notice lag after just 300ms—here's how to stay ahead.
Corbin Montague from Expedia Group shares a comprehensive guide to iOS performance monitoring, covering everything from Apple's native tools to third-party solutions. This is the playbook for teams serious about app quality.
Key Takeaways
- Apple recommends 400ms cold launch: 100ms system init, 300ms for your views
- MetricKit delivers daily performance reports from production users with minimal code
- XCTest metrics can auto-fail CI builds when performance regresses from baseline
- Monitor 7 core metrics: app size, launch time, responsiveness, memory, battery, network, disk I/O
- Xcode Organizer provides free aggregated metrics but only for high-volume apps
iOS developers get three powerful native monitoring tools (XCTest, MetricKit, Xcode Organizer) plus proven third-party options like Firebase Performance, all with implementation examples.
About This Article
iOS apps that use too much memory trigger OS warnings and get terminated, while constant disk writes wear out SSDs faster than they should. Battery drain from inefficient networking and processing means users need to charge more often, which leads them to uninstall the app.
Expedia Group's engineering team uses XCTest Metrics APIs to collect performance baselines automatically during CI/CD workflows. They set up builds to fail when metrics go beyond standard deviation thresholds. They also pull daily production reports from MetricKit and aggregated user data from Xcode Organizer to track memory, battery, and disk usage.
By watching scroll hitch rates and app hangs, teams found that users notice lag delays as small as tenths of a second. This helps them prioritize optimizations. Firebase Performance and SwiftInfo give them cross-platform metrics on network requests and app size, so they can work toward Apple's 400ms target for cold launch times.