Eric Campbell Aug 02, 2025 0 min read Kotlin

Kotlin Coroutines: A Practical Introduction

Coroutines let you write asynchronous code that reads like synchronous code, without callback hell.

Key Insights

Coroutines are lightweight threads managed by the Kotlin runtime, not the OS
Structured concurrency via coroutineScope ensures proper cleanup and cancellation
Flow is Kotlin’s answer to reactive streams, built on coroutines

Basic Coroutines

suspend fun fetchUserData(): User {
    val profile = async { api.getProfile() }
    val posts = async { api.getPosts() }
    return User(profile.await(), posts.await())
}

Structured Concurrency

coroutineScope {
    val deferred = async { heavyComputation() }
    // If this scope is cancelled, deferred is cancelled too
    println(deferred.await())
}

Flow for Streams

fun observePrices(): Flow<Price> = flow {
    while (true) {
        emit(api.getCurrentPrice())
        delay(1000)
    }
}