Mobile App Lifecycle State Persistence

Context

Mobile apps can be interrupted at any time by incoming calls, OS memory pressure, or user actions. A strong engineer should know how to preserve a good user experience when the app is paused, backgrounded, or killed.

Core Question

Explain how you would handle the lifecycle of a mobile application and save state when it is abruptly sent to the background.

Your answer should cover:

1. The major lifecycle transitions relevant to foreground, background, and termination.
2. What state should be saved immediately versus recomputed later.
3. How to design state persistence so the app restores correctly after process death or forced termination.

Scope Guidance

The interviewer expects a practical systems explanation rather than platform-specific trivia. Discuss lifecycle callbacks/events, in-memory vs persistent state, trade-offs around performance and consistency, and common mistakes such as saving too much or relying on background execution guarantees.