Explore declarative configurations for maintaining and reproducing code in this PyCon US talk by Jonathan Striebel. Learn how to future-proof application configs while ensuring backwards compatibility and reproducibility. Gain insights into the application config landscape, covering inputs from CLI arguments, environment variables, and config files, as well as their code representations. Discover serialization, deserialization, type-safety with config-schemas, and evolution techniques. Follow along with practical code examples and recommendations for implementing a maintainable and expressive declarative config system. Access the complete code repository and presentation slides for further reference and implementation.