How much data can UserDefaults store, and how does it work on disk?
Explain UserDefaults as a small plist-backed prefs store covering size limits, async disk writes, suiteName vs standard, and why main-thread access is allowed but not free
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How does Swift's Dictionary work under the hood?
Walk through Swift Dictionary as a CoW hash table — hashing invariants, collisions, complexity traps, nil removal, ordering, concurrency, and key design for senior interviews
How does Swift method dispatch work?
Explain Swift's three method-dispatch mechanisms—static, table (vtable and protocol witness tables), and Objective-C message send—and show when final, value types, and @objc dynamic change which one the compiler uses
What collection types are available in Swift, and when would you use each one?
Explain Swift's protocol-driven collection model, then compare Array, Set, Dictionary, and Range by behavior, complexity, hashing, ordering, copy-on-write, and thread-safety tradeoffs
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