Zomato Android App Development Interview Questions &amp; Answers

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Make sure the query runs off the main thread using suspend or Flow. Use EXPLAIN QUERY PLAN to check for full table scans, and add an @Index on columns used in WHERE, JOIN or ORDER BY. Select only needed columns into a smaller data class instead of SELECT *, page results with Paging 3, and avoid loading large blobs into lists. Wrap bulk inserts in a single transaction.

How do you handle one-time navigation after a successful login in MVVM?

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Recommended practice is to reflect the result in state, such as isLoggedIn = true in UiState, and have the UI react with LaunchedEffect(state.isLoggedIn) to navigate, then the ViewModel marks it consumed if needed. An alternative is a Channel exposed as Flow and collected with lifecycle awareness. Avoid calling navigation directly from the ViewModel, because it should not reference NavController or views.

A ViewModel has grown to 1500 lines handling many responsibilities. How would you refactor it?

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First add tests around current behaviour so refactoring is safe. Then extract business logic into use cases or domain classes, move data mapping into repositories or mappers, and split UI state into smaller, focused data classes. If the screen truly has separate areas, consider separate state holders or child ViewModels per section. Refactor in small pull requests so reviewers can follow and regressions are easy to locate.

The backend team changed a field from a number to a string and the app crashed for all users. How do you prevent this?

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Short term, make parsing lenient for that field, for example with a custom serializer, and handle parse failures without crashing. Long term, agree on API contracts with versioning, use contract tests or a shared OpenAPI schema checked in CI, add ignoreUnknownKeys and default values in kotlinx.serialization, and use remote config or a minimum supported app version mechanism. Monitor parse errors as non-fatal events.

You need to sync 500 images to a server without overloading the network. How would you design it with coroutines?

Zomato Coroutines and FlowHard

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Limit concurrency. Use a Semaphore with withPermit around each upload, or flatMapMerge(concurrency = 4) over a flow of files, or Dispatchers.IO.limitedParallelism(4). Use supervisorScope so one failed upload does not cancel the rest, collect failures for retry with backoff, and report progress through a StateFlow. If the sync must survive app exit, run it inside a CoroutineWorker with WorkManager constraints such as network connected.

Your team wants to migrate a large XML app to Compose. How would you plan it?

Zomato Jetpack ComposeMedium

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Start by setting up a shared Compose theme matching the existing design system, then build new screens in Compose. Migrate leaf components and simple screens next, using ComposeView inside fragments, and leave complex custom views wrapped in AndroidView for later. Measure performance with Macrobenchmark and add Baseline Profiles. Add Compose UI and screenshot tests, train the team, and set a rule that new UI is Compose-only.

What is the difference between @Provides and @Binds in Hilt?

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@Provides is used in a module function that constructs and returns an object, needed for third-party classes like Retrofit or Room that you cannot annotate with @Inject. @Binds is used on an abstract function in an abstract module to tell Hilt which implementation to use for an interface, when the implementation already has an @Inject constructor. @Binds generates less code and is slightly more efficient.

Users who reinstall the app lose all their settings. How can you restore them?

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Android Auto Backup automatically backs up app data to the user's cloud backup account for apps targeting API 23 and above, unless disabled. Configure dataExtractionRules for Android 12 and above to include settings files and exclude tokens or caches. For important data like notes, sync to your own server tied to the user's account, since backup is not guaranteed. Test with adb shell bmgr commands.

Your team is migrating a Java Android app to Kotlin. How would you plan it?

Zomato Kotlin FundamentalsMedium

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Kotlin and Java interoperate, so migrate gradually rather than all at once. Start with new features in Kotlin, then convert leaf classes like models and utilities, writing tests before converting. Add nullability annotations to Java code so Kotlin sees correct types. Review auto-converted code because it often overuses !!. Track progress per module and agree on style rules with ktlint or detekt so the codebase stays consistent.

What does the suspend keyword mean?

Zomato Coroutines and FlowEasy

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suspend marks a function that can pause and resume later without blocking the thread. It can only be called from another suspend function or a coroutine. The compiler transforms it using continuation-passing style into a state machine. suspend alone does not move work to a background thread; the function must use withContext(Dispatchers.IO) or a main-safe library like Retrofit or Room to avoid blocking the main thread.

You need to cache API responses so the home screen opens instantly. What approach do you take?

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Store the response in Room, or a file for a single blob, and have the screen observe the cached data immediately while a refresh runs in the background, known as stale-while-revalidate. Store a timestamp to decide when cache is too old. HTTP caching with OkHttp Cache can also help for GET requests with proper cache headers. Show cached content first, then update smoothly when fresh data arrives.

You are starting a new app for a fintech startup. Which architecture and libraries would you choose and why?

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I would use Kotlin, Jetpack Compose with Material 3, MVVM with unidirectional data flow, Hilt for DI, Coroutines and Flow, Retrofit with OkHttp and kotlinx.serialization, Room for offline data, DataStore for preferences, WorkManager for background sync, and Navigation Compose. For fintech, add certificate pinning considerations, encrypted storage via Keystore, Play Integrity checks, and strong test coverage. Start modular from day one with core and feature modules.

Write an OkHttp interceptor that adds a bearer token to every request.

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class AuthInterceptor @Inject constructor( private val tokenStore: TokenStore ) : Interceptor { override fun intercept(chain: Interceptor.Chain): Response { val token = tokenStore.currentAccessToken() val request = chain.request().newBuilder().apply { if (token != null) header("Authorization", "Bearer $token") }.build() return chain.proceed(request) } } val client = OkHttpClient.Builder() .addInterceptor(authInterceptor) .build()

Your banking app must pass a security audit. What would you check on the Android side?

Zomato Testing, Performance and Play StoreHard

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Check secure storage with Keystore and no secrets in code, TLS only with pinning where justified, no sensitive data in logs, FLAG_SECURE on sensitive screens, root and tamper checks using Play Integrity, exported components reviewed, WebView with JavaScript bridges restricted, R8 obfuscation, session timeout, and biometric authentication with BiometricPrompt and CryptoObject. Use the OWASP MASVS as the checklist and fix findings by severity.

The Play Store rejected your update for a policy violation about permissions. What do you do?

Zomato Testing, Performance and Play StoreMedium

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Read the rejection email and policy centre message carefully to see which permission or declaration failed, often SMS, call log, background location, all-files access or exact alarms. Remove the permission if a less sensitive alternative exists, such as the SMS Retriever API or photo picker. Otherwise update the permission declaration form with a clear use case and video. Check the merged manifest for permissions added by libraries.

Users on slow 2G and 3G networks in small towns report the app keeps failing. How do you improve it?

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Set reasonable connect and read timeouts, retry idempotent requests with exponential backoff, and cache responses so screens show something offline. Reduce payload size with gzip, pagination and fields filtering, and load images in smaller sizes with placeholders. Show clear offline and retry states instead of generic errors. Test with the emulator network throttling and real devices on poor connections, and track failure rates by network type.

Write a Room database class with a migration that adds a column.

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@Database(entities = [NoteEntity::class], version = 2, exportSchema = true) abstract class AppDatabase : RoomDatabase() { abstract fun noteDao(): NoteDao } val MIGRATION_1_2 = object : Migration(1, 2) { override fun migrate(db: SupportSQLiteDatabase) { db.execSQL("ALTER TABLE notes ADD COLUMN pinned INTEGER NOT NULL DEFAULT 0") } } val db = Room.databaseBuilder(context, AppDatabase::class.java, "app.db") .addMigrations(MIGRATION_1_2) .build()

A WorkManager job is not running on some phones from certain manufacturers. How do you investigate?

Zomato Room, DataStore and WorkManagerHard

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Some manufacturers apply aggressive battery optimisations that delay or kill background work. Check the job state with WorkManager's getWorkInfosForUniqueWorkFlow and the background task inspector in Android Studio. Verify constraints are not too strict. Guide users to allow unrestricted battery for the app only where the feature truly needs it, use expedited work for urgent tasks, and use FCM to trigger sync when timely delivery matters.

What is dependency injection and why use Hilt?

Zomato App Architecture, MVVM and HiltEasy

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Dependency injection means classes receive their dependencies from outside rather than creating them, making code testable and loosely coupled. Hilt, built on Dagger, is Jetpack's recommended DI library. It generates code at compile time, provides standard components tied to Android lifecycles (SingletonComponent, ActivityRetainedComponent, ViewModelComponent), and integrates with ViewModels via @HiltViewModel. Errors appear at compile time rather than runtime.

Write a HiltViewModel that exposes a single UiState using StateFlow.

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data class ProductUiState( val loading: Boolean = true, val items: List<Product> = emptyList(), val error: String? = null ) @HiltViewModel class ProductViewModel @Inject constructor( private val repo: ProductRepository ) : ViewModel() { private val _state = MutableStateFlow(ProductUiState()) val state: StateFlow<ProductUiState> = _state.asStateFlow() init { refresh() } fun refresh() = viewModelScope.launch { _state.update { it.copy(loading = true, error = null) } runCatching { repo.fetchProducts() } .onSuccess { list -> _state.update { it.copy(loading = false, items = list) } } .onFailure { _state.update { it.copy(loading = false, error = "Try again") } } } }

How do you build a single-activity app with the Navigation component?

Zomato Android Components and LifecycleMedium

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Keep one Activity hosting a NavHost, and represent each screen as a Compose destination or Fragment. Define routes in a navigation graph, preferably with type-safe routes using Kotlin serialization in Navigation 2.8 and later. Use nested graphs for flows like login or checkout, pop the back stack with popUpTo when finishing a flow, and handle deep links on destinations. This simplifies shared transitions and state handling.

What is the predictive back gesture and how do you support it?

Zomato Android Components and LifecycleHard

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Predictive back, introduced in Android 13 and on by default for apps targeting Android 15, shows a preview of the destination while the user swipes back. Support it by setting android:enableOnBackInvokedCallback="true" and handling back with OnBackPressedDispatcher or BackHandler in Compose instead of overriding onBackPressed, which is deprecated. Navigation libraries and Material components provide animations when you use the supported APIs.

What is a repository and why is it the single source of truth?

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A repository hides where data comes from and gives the rest of the app one API, such as getProducts(): Flow<List<Product>>. With an offline-first design, the repository reads from Room and refreshes from the network in the background, writing results to the database. The UI always observes the database, so it is the single source of truth. This avoids inconsistent copies of data across screens.

Tell me about a time you handled a production crash under pressure.

Zomato Android Components and LifecycleMedium

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Situation: after a release, crash-free users dropped from 99.6 to 97 percent. Task: stop the impact fast. Action: I checked Crashlytics, found a crash on Android 14 caused by a missing foreground service type, paused the staged rollout in Play Console, shipped a hotfix with a test on an emulator for that API level, and wrote a short postmortem. Result: crash rate recovered within a day and we added API-level checks to our release checklist.

What conflict strategies does Room offer for inserts?

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@Insert(onConflict = ...) supports REPLACE, which deletes the old row and inserts the new one; IGNORE, which skips the insert; ABORT, the default, which rolls back the transaction; and others. REPLACE can trigger cascading deletes on foreign keys because it deletes first. @Upsert, added in Room 2.5, inserts or updates without deleting, making it safer for syncing server data into local tables.

How do you build an adaptive layout for phones, foldables and tablets in Compose?

Zomato Jetpack ComposeHard

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Use WindowSizeClass from the Material 3 adaptive library to choose layouts by width class, not device type. On compact width show a bottom navigation bar; on medium use a navigation rail; on expanded use a list-detail layout with ListDetailPaneScaffold or NavigationSuiteScaffold. Avoid locking orientation, since Android 16 ignores orientation restrictions on large screens. Test with resizable emulators and foldable postures.

How do you find and fix memory leaks in an Android app?

Zomato Testing, Performance and Play StoreMedium

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Add LeakCanary to debug builds; it detects retained Activities, Fragments and ViewModels and shows the reference chain. Common leaks are static or singleton references to Context or Views, listeners not unregistered, inner classes holding Activity references, and Fragment view bindings not cleared in onDestroyView. Fix by using application context, lifecycle-aware components and weak references only where needed. Confirm with Memory Profiler heap dumps.

What is Kotlin Flow and how is it different from a suspend function?

Zomato Coroutines and FlowEasy

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A suspend function returns a single value once. A Flow is a cold asynchronous stream that emits multiple values over time, like database updates, location changes or search results. Cold means the code inside flow { } runs only when collected, and runs again for each collector. Room, DataStore and many libraries expose Flow so the UI automatically updates when underlying data changes.

Write a Compose UI test that checks an error appears when login is clicked with an empty email.

Zomato Jetpack ComposeMedium

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@get:Rule val rule = createComposeRule() @Test fun showsErrorForEmptyEmail() { rule.setContent { var state by remember { mutableStateOf(LoginState()) } LoginScreen( state = state, onLogin = { state = state.copy(error = "Email required") } ) } rule.onNodeWithText("Login").performClick() rule.onNodeWithText("Email required").assertIsDisplayed() }

Describe a situation where you had to push back on an unrealistic deadline.