Swift and Kotlin Proficiency Questions

Deep working knowledge of Swift and Kotlin language features, idioms, and trade offs relevant to mobile development. Topics include optional and null safety handling, closures and lambda expressions, generics and type system nuances, protocol and interface patterns, extension and utility methods, functional programming tendencies, automatic reference counting and avoidance of retain cycles, coroutine based concurrency and structured concurrency patterns, error handling models, interoperability with legacy platform languages, and writing idiomatic, testable, and maintainable production code. Candidates should be able to write clear examples, reason about memory and performance implications, and explain language specific best practices.