> This often makes the system brittle to new changes because subsystems have very strict expectations of data schema, even when they don't really need to care a

> This often makes the system brittle to new changes because subsystems have very strict expectations of data schema, even when they don't really need to care about i I deal a lot with this, because I interface with software outside my control. In the case of Rust I find super easy to solve, just use this litte trick: https://serde.rs/attr-flatten.html https://serde.rs/attr-flatten.html #[derive(Serialize, Deserialize)] struct User { id: String, username: String, #[serde(flatten)] extra: HashMap<String, Value>, } Serde is very good. Near all you want is there.