Yes, goroutines are a concurrency mechanism. Actors are also a concurrency mechanism, so I fail to see why the comparison is unfair. As you say, Actors are safe

Yes, goroutines are a concurrency mechanism. Actors are also a concurrency mechanism, so I fail to see why the comparison is unfair. As you say, Actors are safer in that uncaught exceptions in an actor will not bring down a program. They have a few more dials and knobs, you can store references to them, and they are more heavyweight. They have more overhead as can be expected from these facts and this is exhibited in benchmarks like this one. Futures are not a concurrency mechanism precisely. They are a monadic data structure around possibly-concurrent execution. You can wrap a Future around concurrent execution by an Actor, or you can do what you have done and wrap a Future around a sequential recursive computation. As with the synchronous .NET core implementation of the benchmark, the performance is better due to not having the overhead of Actors or other concurrency. Like the synchronous .NET core implementation writing the computation this way is not a fair comparison to the other languages in the benchmark and the high performance does not indicate anything about the efficiency of the concurrency mechanisms available in Scala.