I like to use recursion when I can't predict the number of iterations necessary to do the job. For example, a program that calculates the total size of a folder. With recursion I can easily iterate through all levels of the tree and get their sizes.

I've used the same approach recently when I wrote a GraphQL query generator in Swift. I recursively iterate through an array of dictionaries, each being able to also hold an array of dictionaries of it's own, each being able to also hold an array of dictionaries of it's own, and so on. In the end all I end up with is single a string.

Maybe it's not exactly more efficient, but it was certainly much easier for me.

Recursion is efficient in developer time: it saves you from having to keep track of context yourself because you can just stick it on the call stack.

I don't know of,a case where it's more efficient, but tail recursion is exactly as efficient as iteration, because they compile to the same code. No stack is used and there's no function call overhead. But you need a compiler that knows how to compile tail calls.

I'm doubtful that recursion would ever be more performant than iteration. Iteration with a stack gives you all the capability of recursion without the function call overhead. As others have said, the main advantage of recursion is ease of designing and understanding the solution.

When thinking about hard problems, recursion is often much more efficient than iteration.

not necessarily efficient but here’s my latest use case:

scheduling a health check job recursively. if the health check fails, it schedules itself to run again in X seconds with N-1 runs until giving up and marking the service as down.

iteration here simply wouldn’t work