Rule of thumb of simple. You mark functions with `...

# coroutines

[elizarov]

Rule of thumb of simple. You mark functions with suspend when you expect their implementation to be non-blocking to the invoker thread (aka “asynchronous”). So, if I read your API and see interface Foo { fun doSomethingNetworkRelated() }, then I immediately see that doSomethingNetworkRelated is going to block my thread while it does its network stuff. However, if I see interface Foo { suspend fun doSomethingNetworkRelated() } then I assume that implementation is non-blocking and can be safely used, for example, from my UI thread or from other precious event-loop.