Concurrency interview questions
Scenario-style prompts with sample answer outlines. Focus is on how you would design and reason in real codebases.
- 01Race conditions in structured concurrencyYou have multiple async tasks mutating shared state. How would you design the system to prevent race conditions?
- 02Keeping expensive work off the main threadYou notice UI jank when performing async work. How do you guarantee expensive work never blocks the main thread in a Swift async/await system?
- 03Actor design in a networking and cache stackYou're building a networking layer with caching. Where would you introduce actors, and how would you structure them to avoid contention or bottlenecks?
- 04Cancellation and stale async resultsYou have a screen that fires multiple async requests as the user types (such as search). How do you ensure stale requests don't overwrite newer results?
- 05Bridging legacy GCD to async/awaitYou're working in a large codebase that heavily uses GCD. How would you incrementally migrate it to async/await without breaking behavior?
- 06Task lifecycles in UIKit and SwiftUIHow do you tie the lifecycle of async tasks to a view (such as a SwiftUI view or a UIViewController) so you don't leak work or update deallocated UI?
- 07Debugging concurrency bugsA feature has intermittent crashes or wrong UI state under load. How do you debug suspected concurrency issues before and after they reach production?
- 08Parallelism with async let and task groupsYou need to load several independent resources for a screen. When do you reach for async let vs TaskGroup, and how do errors and cancellation behave?
- 09Task.detached: when it's justifiedWhen is Task.detached the right tool, and what guarantees do you lose compared to structured Task { }?
