>It's still not really concurrency

Well, it also has Workers, which is.

Concurrency != parallelism. You can of course run a multi-process cluster, but that’s besides the point (and these days it’s best to run a single process inside orchestration like k8s).

Basically almost every high performing server atm is running on some form of event loop / cooperative multi-tasking. Ruby Puma, Gunicorn, rust’s tokio and async/await, goroutines... Java is probably the big exception here (if you’re not using VertX et al) and we all know the pain of thread safety.

Very true. Go is an exception, and some day Java will be as well. They're both going route of userspace threads instead of reactive API's, thankfully.