iOS Performance Engineering

When to invoke

• Diagnosing UI slowness, scroll hitches, or app hangs.
• Investigating high memory usage, leaks, or large binary size.
• Wiring MetricKit to receive field performance data from real devices.
• Setting up XCTMetric / measure {} baselines in CI.
• Deciding whether to move work off @MainActor and how to do it safely.
• Evaluating launch time before a release.

Instruments — the primary measurement tool

Never guess at a performance problem; profile first. Instruments ships with Xcode.