> iOS App Performance Checklist
// A developer-focused performance checklist covering launch time, main thread usage, memory, image handling, scrolling, and battery — with guidance on where to measure each one in Instruments.
Performance problems are easier to prevent than to fix after the fact, but they're also easy to overlook when you're focused on features. Most of them follow a short list of patterns: blocking the main thread, loading more memory than the device can comfortably hold, and doing expensive work on every frame of a scroll view.
Instruments is the right tool for all of this. Profiling in debug mode gives misleading results — compiler optimisations are disabled and the simulator does not accurately represent device memory or CPU performance. Always profile in release mode on a real device, ideally one at the lower end of your minimum deployment target.