[Pharo-project] Concurrency in Pharo?

I've been really impressed with what Seaside and Pier were capable of and really wanted to start my new web project with Pharo. I learned that Pharo (and most other open source ST implementations) only use green threads, having no ability to use a multi-core CPU systems. For those of you with experience building mid to heavy load web sites, how do you expect them to scale up on using just one core? Is Pharo a right tool for that? Maybe Pharo (Squeak) has something up its sleeve to handle this, but my heart really sank when I learned about this issue... Thank you, Andrei