iOS Interview Questions 2026

Explain how ARC (Automatic Reference Counting) works in Swift/Objective-C. What is a retain cycle and how do you break one? Give an example using a delegate pattern and explain when to use weak vs unowned references.

Design Apple Pay's tap-to-pay system. When a user taps their iPhone, a payment must complete in under 500ms even with no internet connection. Cover: secure element, tokenisation, NFC protocol, and offline authorisation.

Explain iOS memory management: ARC, strong/weak/unowned references, retain cycles. How does the system handle memory pressure? Walk through what happens when an app receives a memory warning and is then terminated.

Design Siri's speech recognition pipeline. Audio is captured on-device, processed, and a response is returned. How do you split on-device vs server processing to balance latency, privacy, and accuracy?

How does Core Data work in iOS? Explain the managed object context, persistent store coordinator, and the fetch request pipeline. When would you use Core Data vs Realm vs SQLite directly?

An iOS app's scroll performance drops to visibly janky frame rates on a list with complex cells. Walk through your process for diagnosing whether the bottleneck is layout, rendering, or data processing.

How would you design a feature that needs user location data for a core function, while minimizing what leaves the device and remains fully functional if the user denies location permission?