I really love zod in typescript land that bridges the dynamic and static world:
What you do is you declare a schema and it auto-generates a parser that coerces untrusted json data to a type safe object.
The dream later would be that you have an Ecto-like DSL that generates a typesafe cast(...) function similar to the parse function in zod (Basic usage | Zod). This might be worth exploring once types in Elixir land 
A bit off-topic since this isn’t about a specific language feature, but I recently discovered Campfire Write and I’m genuinely impressed by how they’ve tackled the worldbuilding/writing workflow problem for fiction authors.
What makes it stand out is the seamless integration between different creative phases: you can build your world (characters, locations, timeline, magic systems, etc.) and then jump straight into writing with all that context readily available. The UI manages to be both comprehensive and intuitive - no small feat given how complex worldbuilding can get.
The real clever bit is how they handle relationships between elements. Characters can be linked to locations, events to timelines, and it all feels organic rather than database-like. Plus the writing environment itself adapts to show relevant worldbuilding info contextually.
I know it’s probably not built with Elixir, but it’s got me thinking about how Phoenix LiveView could handle this kind of rich, interconnected content management. The real-time updates and stateful components seem like a natural fit for this domain.
Anyway, fascinating to see how they’ve solved the “creative chaos management” problem. Definitely sparking some weekend project ideas! 
Rust has a relational db library that connects to the db while you’re coding and uses the metadata to verify your code at compile-time.
