The rule of thumb I use in most cases: Can it be written statelessly without contortions or large inefficiencies? If so, then I make it stateless. Depending wha

The rule of thumb I use in most cases: Can it be written statelessly without contortions or large inefficiencies? If so, then I make it stateless. Depending what is idiomatic in the language and project, I will usually put it into a function instead of a class. I find stateless code easier to reason about.