Coroutine scope builders

Scope builders—coroutineScope, supervisorScope, withContext—structure concurrent work with parent-child cancellation. Compare with errgroup in Go: failures in one child can cancel siblings when using standard scopes.

Builders overview

• coroutineScope — waits for all children; fails fast if one child throws
• supervisorScope — child failures do not cancel siblings
• withContext(Dispatchers.IO) — switches dispatcher for blocking I/O

runBlocking bridge

Tests often use runBlocking { coroutineScope { ... } } to assert concurrent behavior. Production Android uses viewModelScope or lifecycleScope instead of manual scopes.

Important interview questions and answers

1. Q: supervisorScope use case?
   A: Independent tasks where one failure should not tear down others—e.g. loading multiple UI sections.
2. Q: withContext purpose?
   A: Switch coroutine context (dispatcher, name) for a block—commonly move blocking work off Main.

Self-check

1. Which scope isolates child failures?
2. Why use withContext for database calls on Android?

Pitfall: Never use GlobalScope for app logic—prefer structured scopes tied to lifecycle or request.