You've never needed to share a cache (like a map of ID -> object) across threads? Or implement a queue for distributing work to threaded workers? Or maintain a

You've never needed to share a cache (like a map of ID -> object) across threads? Or implement a queue for distributing work to threaded workers? Or maintain a shared rate limiter across threads, to prevent saturation of some API or other shared resource? Those are all shared memory examples. Avoiding sharing memory for concurrent workers is rare, in my experience, unless the workers are completely isolated -- which they rarely are. You can move some things outside (for example, Redis as a cache), at the expense of performance or simplicity.