I guess what I'm saying is to be judicious about what invariants a particular piece of code should care about, within the context of the larger system. > That'

I guess what I'm saying is to be judicious about what invariants a particular piece of code should care about, within the context of the larger system. > That's right, as the article says you no longer validate data, instead you parse data. Components don't take strings and validate them, they take an EMail address. That doesn't solve the problem, by parsing it my code is caring about its syntax and structure, even if my use case doesn't require that. That creates coupling, and in a distributed system that kind of unnecessary coupling can create major headaches when trying to change things. An even simpler example that many people can empathize with is using strict, closed enums in a distributed system (very easy to do with e.g. Java). Safely adding a new enum value is basically impossible at that point, until you make them "open" enums that can safely parse unknown values. Again I am not disagreeing in principle, I am only saying that this has ergonomic problems in practice and is easy to misuse.