Interview Questions for an iOS Developer

Walk me through how you'd structure a feature using a testable architecture like MVVM or Clean Architecture in Swift.

What to look for: Separates view, presentation, and business logic, makes dependencies injectable and mockable, and explains how the structure keeps the feature testable and the UI thin.

Explain Swift concurrency with async/await, and how it compares to Combine and GCD for a real task.

What to look for: Understands structured concurrency, actors and the main actor, avoiding data races, and chooses the right tool for the job rather than reaching for one pattern reflexively.

How do you implement offline-first data with local persistence using Core Data or SwiftData?

What to look for: Designs a local source of truth, sync and conflict handling, background contexts, and graceful behavior when the network is unavailable.

An app feels janky and slow to launch. How do you diagnose and fix it with Instruments?

What to look for: Profiles startup, main-thread work, and frame drops with Time Profiler and other instruments, finds real bottlenecks like blocking work or retain cycles, and fixes based on data.

How do you craft an interface that follows Apple's Human Interface Guidelines and feels native?

What to look for: References platform conventions, accessibility, dynamic type, safe areas, and standard controls and gestures rather than reinventing platform behavior.

Walk me through managing code signing, build configurations, and an App Store submission.

What to look for: Comfort with provisioning, certificates, schemes and configs, and the review and release process, ideally with CI/CD automating builds.

Tell me about an app you shipped to the App Store. What were you responsible for?

What to look for: Clear ownership, real technical decisions, and an understanding of the full release lifecycle, not just feature coding.

Describe a tough performance or memory issue you tracked down on iOS.

What to look for: Used Instruments and a hypothesis-driven approach, found the root cause such as a retain cycle or main-thread blockage, and verified the fix.

Tell me about a time you handled a crash in production. How did you diagnose and ship a fix quickly?

What to look for: Reads crash reports, reproduces and isolates the cause, ships a targeted fix, and uses monitoring to confirm resolution.

Describe a time you refactored messy or untestable iOS code. What changed?

What to look for: Improved architecture and testability incrementally, justified the refactor, and avoided breaking behavior, ideally backing it with tests.

Tell me about adapting an app for a new iOS version or device, like a major SDK change.

What to look for: Handles deprecations, tests across versions and devices, and balances adopting new APIs against supporting existing users.

An API integration is flaky and sometimes fails. How do you make the app resilient?

What to look for: Adds appropriate caching, retries with backoff, graceful error states and offline fallback, and a good user experience when the network misbehaves.

App startup time has crept up release over release. How do you bring it back down?

What to look for: Profiles cold and warm starts, defers non-essential work off the launch path, reduces main-thread blocking, and measures the improvement with Instruments.

Apple rejects your App Store submission. How do you respond?

What to look for: Reads the rejection against the guidelines, addresses the real issue, communicates with review if needed, and resubmits without guessing or arguing blindly.

You need an offline-capable feature that must reconcile changes when connectivity returns. How do you design it?

What to look for: Local source of truth, change tracking, a sync and conflict-resolution strategy, and clear UI states for syncing and errors.

A SwiftUI screen has a subtle layout or state bug that's hard to reproduce. How do you approach it?

What to look for: Reasons about state and view identity, isolates the state driving the issue, uses previews and debugging tools, and forms a testable hypothesis.

How do you collaborate with designers to deliver polished, platform-appropriate interfaces?

What to look for: Translates designs faithfully while applying platform conventions and accessibility, and pushes back constructively where designs fight the platform.

How do you approach code review on an iOS team?

What to look for: Reviews for correctness, architecture, testability, and platform best practices, gives constructive feedback, and values shared conventions.

How do you decide when to adopt a new Apple API versus stick with a proven approach?

What to look for: Weighs minimum supported versions, stability, and user impact, and avoids chasing novelty at the cost of reliability.

How do you keep crash rates and quality high across a fast release cadence?

What to look for: Uses crash monitoring, automated tests, CI/CD, and staged rollouts, treating quality as continuous rather than a final gate.