I'm not normally a stickler for HN's rule about title preservation, but in this case the "in distributed systems" part is crucial, because IMO the urge to use both the actor model (and its relative, CSP) in non-distributed systems solely in order to achieve concurrency has been a massive boondoggle and a huge dead end. Which is to say, if you're within a single process, what you want is structured concurrency ( https://vorpus.org/blog/notes-on-structured-concurrency-or-g... ), not the unstructured concurrency that is inherent to a distributed system.
It was a theme in part of my career to pick up something written in Scala that used actors that (1) didn't always get the same answer and (2) didn't use all the CPU cores and struggling for days to get it working right with actors then taking 20 minutes to rewrite it using Executors and getting it to work the first time and always work thereafter.