If you’ve been using coroutines for a while, you probably feel comfortable with launch, async, dispatchers and structured concurrency. But under the surface, all of that suspend magic boils down to one simple idea: continuation.
In this article, I’ll walk through the Continuation interface, how the Kotlin compiler rewrites suspend functions into state machines, and how those pieces fit together at runtime.
Quick recap: what suspend actually does
When you mark a function with suspend keyword, you’re telling the compiler:
This function might pause and resume later, but from the caller’s perspective it should look like a normal call returning T.
A few important properties:
A suspend fun can pause at suspension points (like delay, await) without blocking the thread.
When it resumes, it continues as if it had never left; locals and the position in the function are restored.
