Yes; in many cases, if there are two tasks that hold some piece of data, the compiler cannot, at compile time, when to free that data, as it doesn't know which of the two tasks will finish first.

That means the lifetime of that object must be tracked at runtime, with a garbage collector. This is where you get Arc (or shared-ptr).

I'm not sure how you would safely solve this in C++, but FWIW, scylladb is a high performance database that also makes use of shared_ptr.