Role interview guide
Mobile developer interview questions and what to expect
Mobile developer interviews usually go deep on one platform (Android with Kotlin, iOS with Swift, or a cross-platform framework such as Flutter or React Native) and on how apps behave on real devices: lifecycles, memory, offline use and slow networks. Candidates commonly report a coding round or a take-home building a small app, and for experienced roles, questions on app architecture and releasing through the app stores.
What candidates commonly report; it varies by employer, level and country. Last reviewed 18 October 2026.
The usual stages
- 1Recruiter or HR screen
- 2Coding test or take-home: often a small app that loads data from an API and shows it
- 3Platform interview: lifecycle, UI, threading, storage and the platform's own tools
- 4Coding or problem-solving interview, sometimes general rather than mobile-specific
- 5App architecture or design discussion for experienced roles
- 6Hiring manager or behavioural round
What interviewers check
- Depth in one platform's lifecycle and UI toolkit
- Keeping the main thread free so the app stays responsive
- Handling offline use, poor networks and the app being restarted
- A clear architecture that separates UI, state and data
- Care with battery, memory and app size
- Experience shipping and supporting an app in the stores
Behavioral questions
Tell me about a crash that reached users. How did you find the cause and fix it?
A good answer covers
- How you learned of it: crash reports, store reviews, support tickets
- How you reproduced it: device, OS version, the exact steps
- The fix, how you got it out quickly, and how you prevented similar crashes
Describe a time you had to support older devices or OS versions while adding a new feature.
A good answer covers
- The constraint and how many users it affected
- How you handled it: fallbacks, version checks, raising the minimum version
- The trade-off you agreed with the team
Tell me about a release that didn't go to plan, such as a store rejection or a broken update.
A good answer covers
- What went wrong and how you found out
- What you did to recover, and how quickly
- What you changed in your release process: checks, staged rollouts, feature flags
Tell me about a time you worked with a designer to make an app feel right on its platform.
A good answer covers
- Where the design clashed with or followed the platform's conventions
- How you agreed the changes
- How users responded
Questions about the job
Explain the lifecycle of an Android Activity or an iOS view controller, and a bug that comes from getting it wrong.
A good answer covers
- The main states, and when the system creates, pauses or destroys a screen
- Saving and restoring state, such as on an Android rotation or when the system ends the app in the background
- A bug example: work continuing after the screen has gone, or lost user input
Why must network and disk work stay off the main thread, and how do you do that on your platform?
A good answer covers
- The main thread draws the UI; blocking it causes freezes and 'not responding' errors
- Coroutines, Swift concurrency, Dart futures or background queues
- Returning results to the main thread safely, and cancelling work when a screen closes
How would you make an app work well offline and sync when the connection returns?
A good answer covers
- A local database as the source the UI reads from
- Queueing changes made offline and sending them later
- Handling conflicts when the same data changed on the server meanwhile
Your app's memory use keeps climbing as users move between screens. How would you find out why?
A good answer covers
- Using the platform's memory profiler to see which objects stay alive
- Common causes: listeners never removed, references to closed screens, oversized images
- Fixing it and checking the memory graph again
Compare architecture patterns such as MVVM and MVI. Which do you use, and why?
A good answer covers
- What each separates: UI, state, logic and data
- How the pattern makes testing and changes easier
- An example from your own app, and the pattern's downsides
How would you show a long, scrolling list of images smoothly?
A good answer covers
- Lists that only build visible rows, such as RecyclerView, LazyColumn, UICollectionView or Flutter's ListView.builder
- Loading and caching images at the right size, off the main thread
- Placeholders, and cancelling loads for rows that scroll away
Native or cross-platform: how would you choose for a new app?
A good answer covers
- Team skills, time to market and the value of one codebase
- Performance, access to platform features, and how native it must feel
- Your own experience of the trade-offs
How would you store a user's login token securely on the device?
A good answer covers
- The Keychain on iOS and Keystore-backed storage on Android, not plain preferences
- Short-lived tokens with refresh, cleared on logout
- Never logging tokens or shipping secrets inside the app
Talk me through how you'd set up push notifications that open the right screen in the app.
A good answer covers
- Registering the device token with your server and keeping it current
- Deep links, and handling the app being closed, in the background or open
- Asking for permission at a sensible moment and not over-sending
Users say the app takes too long to open. How would you investigate and speed up start-up?
A good answer covers
- Measuring cold and warm start times on a mid-range device
- Delaying work that the first screen doesn't need
- A lighter first screen, fewer libraries set up at launch, and measuring again
How do you test a mobile app, and what do you test on physical devices rather than emulators?
A good answer covers
- Unit tests for logic and UI tests for the key flows
- Physical devices for performance, camera, sensors, push and different screen sizes
- Beta testing and staged rollouts before a full release
Motivation and fit
Why mobile development? Which app do you admire, and why?
A good answer covers
- What draws you to mobile: building for the device in people's hands, the craft, the platform
- A specific app and one detail it gets right
- Something you'd like to build
What would you improve first in our app, and how would you know it helped?
A good answer covers
- A specific issue you noticed while using the app
- The change and what it would cost to build
- A metric such as ratings, crash-free sessions or retention
Tips
- Install and use the company's app before the interview; note one thing you like and one you'd improve.
- Pick one platform and go deep; interviewers usually value real depth in Kotlin or Swift over a little of everything.
- Keep an app you can demo on your phone or in the store, and know its architecture well.
- When you describe any feature, mention what happens offline, on rotation or when the app is killed; those cases set strong answers apart.
- Know your platform's profiling tools by name and what you've used them to find.
Practise it out loud
A mock interview asks what mobile developer interviews usually test, follows up on your answers and gives you a report. The warm-up is free, needs no account and checks five of these questions as you answer.
About this guide
Written by Orbit from what candidates and interviewers commonly describe for this kind of job. The questions are Orbit's own practice questions, not questions taken from any employer's interviews. Processes change, so check the job post and what your recruiter tells you.