Interview guides / ios

Netflix-Style iOS Interview Questions

What Netflix-style iOS interviews often emphasize: performance, streaming clients, offline resilience, architecture, and coding quality. Unofficial prep guide.

This is unofficial prep. Company processes change, and AceMobileInterview is not affiliated with Netflix.

Large consumer apps typically probe performance under media-heavy UI, networking at scale, thoughtful architecture, and clean coding. Prepare to discuss image/video pipelines, caching, and hitch-free lists.

Use these prompts to practice senior mobile judgment, then deepen with AceMobileInterview projects and system design.

1. 1.How would you keep a media-heavy feed scrolling at 60fps?

   Stable cell identities, async image decode at display size, bounded concurrency, prefetch near viewport, avoid main-thread JSON/image work, and measure with Instruments hitches. Cache aggressively but evict under memory warnings.

2. 2.Design the iOS client for personalized home rows with mixed media.

   Row ViewModels over a repository that merges cached shelves with network refresh. Prefetch next shelves. Separate image/video pipelines. Feature flags for experimental rows. Degrade to cached shelves offline with clear freshness indicators.

3. 3.How do you handle flaky networks during playback-related API calls?

   Timeouts, retries with jitter for idempotent GETs, circuit-breaking for non-critical personalization, offline cache for continue-watching style metadata, and user-visible retry. Never block core playback shell on non-critical calls.

4. 4.Walk through the UIViewController lifecycle and where you would load data, configure UI, and clean up observers.

   loadView → viewDidLoad (one-time setup) → viewWillAppear → viewIsAppearing → viewDidAppear → viewWillDisappear → viewDidDisappear → deinit. Load remote data after first appear or via a dedicated loader; remove NotificationCenter/KVO observers in deinit or viewDidDisappear depending on scope; cancel in-flight tasks when the screen disappears if results are no longer needed.

5. 5.When do you pick delegate patterns vs completion closures?

   Delegates suit multi-method ongoing relationships (tableView). Closures suit one-shot results. Avoid retain cycles: weak delegates, weak self captures.

6. 6.What does iOS sandboxing restrict?

   Apps can’t freely read other apps’ data; limited filesystem, entitlements for capabilities (iCloud, push, associated domains). Privacy manifests/permissions gate sensitive APIs.

7. 7.What are common NotificationCenter bugs and how do you avoid them?

   Forgetting to remove observers (pre-block API), posting on wrong threads, overusing global events. Prefer Combine publishers, delegates, or scoped observers; always consider lifecycle.

8. 8.What is KVO and what replaced it in many Swift codebases?

   KVO observes Obj-C property changes. Prefer Combine, Observation/@Observable, delegates, or closures for Swift-first code. KVO still appears with AVFoundation and legacy APIs.

9. 9.How does cell reuse work and what bugs does it cause?

   Cells dequeue from a reuse pool; configure every visible field in cellForRow or configure methods. Stale images/text appear if you don’t reset state; cancel image loads on prepareForReuse.

10. 10.When would you use Result<Success, Failure> instead of throws?

    Result is great for async callbacks and stored outcomes. throws fits synchronous APIs and async/await. You can bridge with get() / mapError depending on call site style.

11. 11.How do optionals work, and when would you use ?, !, if let, guard let, and ??

    Optionals wrap absence of a value. Prefer if let/guard let for safe unwraps; ?? for defaults; avoid force unwrap (!) except when truly impossible to be nil. Optional chaining (?.) short-circuits safely.