Interview practice

Mobile Developer (React Native)

0–2 years · Junior — React Native · JavaScript · Native modules · Offline storage · App release · Performance

scenario Crash handling 1 of 6

You are notified that users are experiencing random crashes in the app. How do you begin to investigate the issue?

What a strong answer covers

Collects crash logs from users or analytics tools; reproduces the issue on different devices and scenarios; checks for common patterns in the reported crashes; reviews recent code changes or dependencies; isolates components that may be causing instability.

The follow-up you would get

The crash logs indicate a memory leak. What steps would you take to identify and resolve this?

Could you have answered that?

ownership A technical failure 2 of 6

Tell me about a time when a performance issue arose after a release, and what steps you took to resolve it.

What a strong answer covers

Specifies the performance issue and its impact on users; outlines the monitoring tools used to identify the problem; details the immediate actions taken to mitigate the issue; explains any long-term solutions implemented; reflects on lessons learned about performance testing pre-release.

The follow-up you would get

What could you have done to catch it earlier?

Could you have answered that?

technical Debugging 3 of 6

You encounter a crash when navigating between screens in your React Native app. What steps do you take to troubleshoot this issue?

What a strong answer covers

Enables error boundaries to capture errors; reviews console logs for stack traces; uses React Native Debugger to inspect the application's state; isolates the issue by narrowing down to specific components; tests with different navigation libraries if applicable.

The follow-up you would get

What if the logs don't provide enough information to identify the cause of the crash?

Could you have answered that?

scenario App release 4 of 6

You are preparing for a hotfix release to address a critical bug. What immediate actions do you take to ensure a smooth release?

What a strong answer covers

Confirms the bug fix is verified with test cases; updates versioning and changelog appropriately; performs regression testing to catch related issues; ensures that build configurations are set for production; prepares a rollout plan with monitoring for immediate feedback.

The follow-up you would get

Once released, users report a new issue introduced by the hotfix. How do you handle this situation?

Could you have answered that?

scenario Performance 5 of 6

During testing, the app takes too long to load the initial screen. How do you approach identifying the cause of this delay?

What a strong answer covers

Analyzes the bundle size and checks for unnecessary imports; profiles the app startup to identify bottlenecks; reviews any synchronous code blocking the main thread; evaluates image sizes and loading methods; considers lazy loading for non-essential components.

The follow-up you would get

After optimising, the load time improves but is still not ideal. What additional strategies could you implement?

Could you have answered that?

technical React Native performance 6 of 6

A React Native app is experiencing lag when scrolling through a list of 1000 items. What steps do you take to identify and resolve this issue?

What a strong answer covers

Profiles the app using React Native Performance Monitor; checks for unnecessary re-renders by using React.memo or PureComponent; considers optimising the FlatList component by using getItemLayout; verifies the use of native driver for animations; evaluates the performance of image loading and caching strategies.

The follow-up you would get

If using FlatList didn't improve performance, what other rendering strategies could you apply?

Could you have answered that?

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