Well it is trite to say it but Haskell has many examples of servers and idiomatic haskell will almost always use immutable data. Examples are web frameworks lik

Well it is trite to say it but Haskell has many examples of servers and idiomatic haskell will almost always use immutable data. Examples are web frameworks like Yesod and web servers like Warp. I'm working on a toy stock exchange app to learn haskell and of course it will be mostly immutable. It will use some shared global state. This will have mutable reference using mvars or transactional memory but the "objects" themselves will be immutable. Communicating between threads makes total immutability hard (maybe impossible?) unless you have a very clever threading model.