There’s plenty of real-world FP systems written in Scala. In general, FP is not a problem today, because data mutation usually happens in some kind of external

There’s plenty of real-world FP systems written in Scala. In general, FP is not a problem today, because data mutation usually happens in some kind of external database, and the programs people have to write are just stateless transformations of incoming requests (http or other kinds, depending on the application).