Topic
Concurrency
Modern Swift concurrency, synchronization tradeoffs, and the reasoning interviewers expect around safety and performance
Focus areas: Actors, structured concurrency, cancellation, data-race prevention
When would you choose a Swift actor over a serial DispatchQueue?
Compare language-level isolation with traditional queue-based synchronization in production iOS code
What concurrency problems should you know in Swift?
Distinguish race conditions, data races, priority inversion, deadlock, and actor reentrancy anomalies with short Swift examples and practical fixes
On which thread does Swift call deinit?
Explain that deinit runs where the last strong reference is released, then connect that rule to UI safety, MainActor isolation, and isolated deinit
How do you make shared mutable state thread-safe in Swift?
Start with the race condition, then compare locks, semaphores, queues, barriers, and actors for protecting shared mutable state in real Swift code
How do task groups differ from async let in practical iOS code?
Explain when fixed child tasks make `async let` the better tool, and when dynamic fan-out or incremental result handling pushes you to task groups