Explore interface-driven design techniques for building robust and maintainable Julia systems in this JuliaCon 2024 conference talk. Learn how to leverage tools like RequiredInterfaces.jl, BinaryTraits.jl, and Interfaces.jl to define, check, and dispatch on interfaces or traits. Discover the benefits of functional coding style and its interplay with interface-driven design. Examine exemplar packages like ChainRulesTestUtils.jl and GeoInterface.jl to understand robust interface testing and creating powerful common languages for package interoperability. Gain insights into managing complexity in large codebases, improving developer productivity, and reducing runtime errors to logical issues. Understand the process of developing effective interfaces that capture the essence of a problem by separating the "what" from the "how" of functions.