Advanced everything in Mobile Dev, page 9
Explain `inline` and `reified` in Kotlin
Tests your grasp of JVM performance costs and type erasure. A great answer explains how inline avoids object allocation for lambdas, and how this enables reified to bypass type erasure for runtime checks. A red flag is just saying 'it's for performance'.
Compare and contrast Kotlin's `apply` and `let` scope functions
This tests your grasp of idiomatic Kotlin scope functions. apply uses this and returns the object, ideal for configuration. let uses it and returns the lambda result, useful for null-safe chaining.
When would you use a sealed class instead of an enum?
This tests your understanding of state representation. Explain that sealed classes define a hierarchy of types that can hold different data, while enums are a set of singleton constants.
Coroutine Exception Handling: launch vs. async
Coroutine builders handle exceptions differently. launch propagates them immediately, crashing if unhandled. async silently catches them, waiting for you to call await. Use a CoroutineExceptionHandler on root scopes for global logging.
How do you diagnose and fix excessive recomposition in Jetpack Compose?
This tests your understanding of Compose's stability system for performance. Use the Layout Inspector and Compiler Metrics to find unstable composables, then fix them with immutable data types and stable lambdas.
remember vs. rememberSaveable: When and Why to Use Each
Tests understanding of Compose state survival. remember is for recomposition scope. rememberSaveable survives activity recreation and process death via a Bundle, requiring custom Savers for complex types. Red flag: saying remember survives rotation.
How does Android manage a ContentProvider's lifecycle during a query?
This tests your understanding of Android IPC and component lifecycles. Explain how ContentResolver uses a URI to have the system instantiate the provider in its own process.
Bound Service Lifecycle: Config Changes and Multiple Clients
Tests deep knowledge of bound service lifecycles. A config change causes an unbind/rebind cycle, recreating the service. With multiple clients, the service isn't destroyed until the last one unbinds. Red flag: assuming the service survives the config change.
Handle Android Process Death vs. Configuration Changes
Tests your grasp of Android's lifecycle for state restoration. A good answer explains that onCreate(savedInstanceState) is called in both cases, but process death recreates everything. Use ViewModel with SavedStateHandle.
How would you manage API keys in Gradle without version control?
Tests secure credential handling in Android builds. A good answer proposes the Secrets Gradle Plugin, which reads from an untracked properties file and exposes keys via BuildConfig, while also noting this doesn't protect against APK decompilation.
How do you diagnose a memory leak with Android Studio Profiler?
This tests your systematic process for debugging memory issues. A good answer outlines using the Memory Profiler, forcing GC, capturing heap dumps, and analyzing object references. A red flag is just naming the tool without explaining the 'how'.
Gradle Build Types vs. Product Flavors
This tests your understanding of Gradle's build matrix for creating different app versions. A great answer defines build types (how it's built) vs. flavors (what is built) and explains that variants are the cross-product. A red flag is confusing their roles.
Implement a type-safe DSL in Kotlin for a UI component
Tests understanding of Kotlin's type-safe builders via lambdas with receivers. A great answer defines model classes, creates a top-level builder function taking a Receiver.() -> Unit lambda, and defines nested builder methods.
Explain Kotlin's `reified` type parameters and their use case
Tests your grasp of JVM type erasure and Kotlin's solution. A great answer defines reified as making a generic type's Class accessible at runtime, explains this requires an inline function to substitute the type at the call site, and shows an example.
How does coroutine cancellation work internally?
This tests your grasp of cooperative cancellation. Explain that cancel() sets a flag, causing a CancellationException at the next suspension point. A non-suspending loop must explicitly check isActive to stop.
Explain backpressure in Kotlin Flows and its management operators
This tests your understanding of Flow's sequential nature and strategies for decoupling producers and consumers. Explain default suspension, then detail buffer(), conflate(), and collectLatest(). A red flag is confusing conflate() with collectLatest().
What problem does `inline` solve, and how does `reified` relate?
This tests your grasp of Kotlin compiler optimizations and JVM type erasure. Explain that inline eliminates the runtime overhead of lambda objects. Then, describe how reified leverages inlining to make generic types accessible at runtime.
Compare and contrast `apply` and `let` scope functions
Tests Kotlin scope function knowledge: context (this/it) & return value. apply uses this, returns the object (for config). let uses it, returns lambda result (for null-checks/transforms). Red flag: mixing up return values or use cases.
When to use a sealed class instead of an enum?
Tests your grasp of Kotlin's type hierarchies. Use sealed class for states with associated data (e.g., Success(data)), as subclasses can have unique properties. Use enum for simple, constant states. A red flag is treating them as interchangeable.
CI/CD for React Native: Automating App Releases
CI/CD for React Native is an assembly line for your app, taming the complexity of managing JS, Android, and iOS code. It automates builds on every push and deploys to stores. The main footgun is storing signing keys directly in your repo instead of using.
We are hiring for this. Every open role lists the topics its interview covers, so you can prepare for the real thing rather than guessing.
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