Context

Mobile engineers at American Express Global Business Travel often need to load Egencia trip details, traveler profiles, and policy data without blocking the UI. This question evaluates whether you can explain Swift concurrency clearly and apply it to production app flows.

Core Question

Explain how you handle asynchronous programming in Swift.

Address these points:

1. How do async/await, Task, and structured concurrency work in Swift?
2. How do you run multiple independent requests concurrently and then combine the results?
3. How do you handle cancellation, errors, and UI updates safely, especially on the main thread?

Scope Guidance

The interviewer expects a practical engineering explanation rather than language trivia. Discuss the core concurrency model, common APIs, trade-offs versus older callback-based approaches, and how you would structure code in an iOS app that fetches multiple pieces of Egencia data.