Mobile Developer Interview Questions 2026
Questions that test platform-specific knowledge, performance optimization, and cross-platform architecture decisions.
10 questions3 categoriesWith answer hints
Technical
4 questions1What is the difference between the Activity lifecycle and Fragment lifecycle on Android, and why does it matter?
Hint: Activity lifecycle controls the full screen; Fragment lifecycle is nested within it. Fragment can be added/removed without destroying the Activity. Misunderstanding leads to memory leaks and state loss on rotation.
2How does Swift's ARC (Automatic Reference Counting) work, and how do retain cycles cause memory leaks?
Hint: ARC deallocates objects when their reference count hits zero. Retain cycles: two objects hold strong references to each other, preventing deallocation. Fix: mark one side as `weak` or `unowned`.
3What is the difference between React Native's new architecture (JSI/Fabric) and the old bridge?
Hint: Old bridge: asynchronous JSON serialization between JS and native. JSI: synchronous C++ interface, eliminating bridge overhead. Fabric: new renderer enabling synchronous layout and better concurrency.
4How do you handle offline-first data synchronization in a mobile app?
Hint: Cover local storage (SQLite, Room, Core Data), sync strategy (last-write-wins vs CRDTs for conflict resolution), exponential backoff for retry, and user-facing feedback for sync state.
Behavioral
3 questions5Tell me about the most challenging performance problem you solved in a mobile app. What was the root cause?
Hint: Common causes: janky scroll (main thread work), large images without caching, excessive re-renders in React Native. Show profiling approach (Instruments, Android Profiler, Flipper) and measurable improvement.
6Describe a time you had to make a major architectural decision for a mobile app. What were the tradeoffs?
Hint: Cover the decision context (native vs cross-platform, MVC vs MVVM vs TCA), what you evaluated, who you consulted, and what you learned post-implementation.
7Tell me about a time you collaborated with a backend engineer to design an API that served mobile clients well.
Hint: Mobile-specific concerns: offline-first design, pagination, partial response fields, versioning, push notification tokens. Show you advocated for mobile constraints in the API design process.
System Design
3 questions8Design a mobile app architecture for a social media app with a feed, direct messaging, and media uploads.
Hint: Cover clean architecture (data/domain/presentation layers), repository pattern, feed pagination (cursor-based), WebSocket or APNS/FCM for messages, background upload with resume capability.
9How would you design an offline-capable note-taking app that syncs across devices?
Hint: Local SQLite/Core Data as source of truth, CRDT or operational transform for conflict resolution, sync protocol design (delta sync vs full sync), background sync scheduling, and end-to-end encryption.
10Design a push notification system that supports personalized, timely notifications for 10 million users.
Hint: Cover APNs/FCM gateway, notification service with audience targeting, user preference store, frequency capping, A/B testing for copy, delivery confirmation, and opt-out compliance.
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View Mobile Developer RoadmapQuestions reflect commonly asked interview topics for Mobile Developer roles across companies of various sizes. Hints summarize what strong answers typically cover — use them as a preparation guide, not a script.