Kotlin fundamentals questions
"Key differences between Kotlin and Java for Android development?" Kotlin is Android's primary language since 2019. Improvements: null safety in the type system, extension functions, coroutines for async programming, data classes, and concise syntax. Java interoperability is seamless.
"Explain Kotlin coroutines and coroutine builders." Coroutines are lightweight concurrency primitives that suspend without blocking a thread. launch is fire-and-forget (no return value). async returns a Deferred (use .await() to get the result). Use viewModelScope in ViewModels and lifecycleScope in Activities/Fragments so coroutines cancel automatically with the lifecycle.
Android architecture questions
"Explain MVVM with Jetpack components." ViewModel: holds UI state, survives configuration changes, emits updates via StateFlow. View (Activity/Fragment/Composable): observes ViewModel state and renders it, sends user events to ViewModel. Repository: abstracts data sources (Room, Retrofit). The key invariant: View never accesses Model directly, ViewModel never references View. This is Google's officially recommended architecture.
"LiveData vs StateFlow?" LiveData is lifecycle-aware and stops delivering values when the observer is inactive. StateFlow is Kotlin-first, requires repeatOnLifecycle for lifecycle awareness, and integrates naturally with Jetpack Compose. StateFlow is the modern choice for new code.
Jetpack Compose questions
"Explain recomposition in Jetpack Compose." Recomposition is Compose re-executing composable functions when their state changes. Compose only recomposes functions whose inputs changed. To minimise unnecessary recomposition: use remember to preserve state, derivedStateOf for computed values, pass only the data each composable needs, and use key for composables in loops.
How to prepare
The 2026 Android interview bar expects: Kotlin with coroutines and Flow, Jetpack Compose for UI, MVVM with Hilt for dependency injection, Room for local data, and Retrofit for networking. Build a complete app using all of these. Review Google's official Android architecture samples — interviewers draw questions directly from them. Know how to write unit tests for ViewModels with JUnit and coroutine test utilities.