If a function already calls a suspend function, must it be marked as a suspend function itself?

When a function in Kotlin calls a suspend function, it does not necessarily have to be marked as a suspend function itself. The key distinction lies in how suspension works in Kotlin. A suspend function can be called from within a coroutine, and if a function is not suspended but rather operates synchronously, it can still invoke the suspend function using a coroutine builder.

In practical terms, if you have a regular function that needs to execute a suspend function, you can create a coroutine within that regular function to handle the suspension appropriately. This means the outer function can remain a traditional function without the suspend modifier, allowing flexibility in using suspend capabilities without imposing coroutine restrictions beyond where they are necessary.

This principle allows developers to build clean and efficient code by only marking functions as suspend where it's specifically needed, rather than forcing every caller up the call chain to also be suspend functions, thereby simplifying function signatures and maintaining code readability.