Practice Prompts

A search field fires a query on every keystroke. Make it only query after the user pauses typing for 300ms, and cancel the in-flight query when a new keystroke arrives — using Swift concurrency, no Combine.

Many view tasks request images concurrently. Build an in-memory cache that never races, and that de-duplicates concurrent requests for the same URL so it only downloads once.

An API returns snake_case keys, ISO-8601 dates, and a nested object. Decode it into clean Swift models without hand-writing every key.

Wrap an async operation so it retries on failure up to N times with exponential backoff, respects cancellation, and rethrows the last error if all attempts fail.

Build a view model that loads a list and exposes loading / loaded / empty / error states so the view can render each cleanly. Make it testable.

A profile screen needs the user and their posts from two endpoints. Fetch them in parallel and combine — don't await one then the other.

Store and read an auth token securely. Explain why this belongs in the Keychain rather than UserDefaults.

You have a legacy load(completion:) that returns a Result. Expose a modern async throws version without rewriting the legacy code.

Render a long list that loads the next page as the user nears the bottom, without loading everything up front and without firing duplicate page requests.

Users create and edit notes that must work fully offline and sync across devices. Design the data flow, sync strategy, and conflict resolution.

A single-target app has 12-minute incremental builds and constant merge conflicts. How do you restructure it so a large team can move fast?

Design a social feed of high-resolution photos that scrolls at a steady frame rate on older devices and doesn't blow the memory budget.

Design the layer between your UI and the backend: how requests, decoding, caching, auth refresh, and testing fit together.

Design navigation for a multi-tab app that must support deep links, push-notification routing, and state restoration.

Set up build, test, signing, and release for a team so every change is verified and shipping is one click — with a safe rollout.

Let users search their content by meaning, not just keywords, entirely on device for privacy. Design it.