Kotlin Coroutines & Flows

Patterns for structured concurrency, Flow-based reactive streams, and coroutine testing in Android and Kotlin Multiplatform projects.

When to Activate

• Writing async code with Kotlin coroutines
• Using Flow, StateFlow, or SharedFlow for reactive data
• Handling concurrent operations (parallel loading, debounce, retry)
• Testing coroutines and Flows
• Managing coroutine scopes and cancellation

Structured Concurrency

Scope Hierarchy

Application
  └── viewModelScope (ViewModel)
        └── coroutineScope { } (structured child)
              ├── async { } (concurrent task)
              └── async { } (concurrent task)

Always use structured concurrency — never GlobalScope:

// BAD
GlobalScope.launch { fetchData() }

// GOOD — scoped to ViewModel lifecycle
viewModelScope.launch { fetchData() }

// GOOD — scoped to composable lifecycle
LaunchedEffect(key) { fetchData() }

Parallel Decomposition

Use coroutineScope + async for parallel work:

suspend fun loadDashboard(): Dashboard = coroutineScope {
    val items = async { itemRepository.getRecent() }
    val stats = async { statsRepository.getToday() }…