I'm not sure what you're saying here exactly. What is unsuitable for real-world applications? I will say this, though, regarding the need for shared, mutable s

I'm not sure what you're saying here exactly. What is unsuitable for real-world applications? I will say this, though, regarding the need for shared, mutable state: You can communicate by sharing memory, but you can also share memory by communicating. This is I guess what you allude to with database-only state, but it doesn't need to be a database. It could just as easily be a memcached server or some other fase key-value store.