Android Architecture

viewModelScope is tied to a ViewModel and cancelled in onCleared(). lifecycleScope belongs to an Activity or Fragment, cancelled on onDestroy. Both exist so no coroutine outlives the component that started it — hence not GlobalScope.

A ViewModel is scoped to the ViewModelStoreOwner, so it survives a configuration change: on rotation the Activity is recreated, the ViewModel is not. It does not survive process death — the OS kills the process and its memory. Hence SavedStateHandle.

Use WorkManager for deferrable, guaranteed work that must survive process death and app restarts — it persists and reschedules. Use a foreground Service for user-visible work that must run right now and continuously, like media playback or a watched upload.

The repository is the single entry point to a feature's data: it owns the network and database sources, decides which answers a request, and exposes domain models upward. The ViewModel never sees Retrofit or Room — so you can test it with a fake.

Each scope owns a parent Job, so cancelling the scope cancels every child coroutine, nested ones included. lifecycleScope is cancelled on every Activity/Fragment destruction, so a rotation kills it; viewModelScope survives that and is cancelled only in onCleared(). Work that must outlive a rotation belongs in viewModelScope.

In MVVM the ViewModel owns several independent state holders and the view calls its methods directly — less ceremony, but fields can drift out of sync mid-update. MVI routes every action through one intent stream into a reducer emitting a single immutable state, so each frame is consistent and a bug replays from the log; the price is boilerplate. With these interacting fields, choose MVI.

The hand-made scope is never cancelled, so its collecting coroutine outlives onDestroyView and keeps holding binding — one dead view hierarchy is retained per visit. Collect from viewLifecycleOwner.lifecycleScope inside repeatOnLifecycle(STARTED), which is cancelled when the view dies, or cancel the scope yourself in onDestroyView.

SavedStateHandle is a key-value map backed by the saved-instance Bundle the system writes before killing the process, so its entries are restored into the recreated ViewModel. A plain ViewModel field lives only in RAM and is gone. It is Bundle-sized: keep small identifiers there — a query, a selected id — and re-load the data from the repository.

Enqueue a PeriodicWorkRequest for a CoroutineWorker carrying Constraints for an unmetered network and charging; WorkManager persists the request in its own database, so it survives process death and reboot. Dedupe with enqueueUniquePeriodicWork(KEEP). Return Result.retry() on a 503 to get exponential backoff and Result.failure() on a 401. doWork is suspend, so it is cancelled when a constraint stops holding.

Use WorkManager with a long-running worker promoted via setForeground (which posts the required ongoing notification). It persists the job, so it survives process death and reschedules to resume after a kill. Doze allows a foreground worker to keep running. Report progress with setProgress, observed via a WorkInfo LiveData/Flow in the UI.