Magnar Sveen, a seasoned Clojure programmer from Norway, dives into the Functional Core, Imperative Shell (FC/IS) architecture. He explains how this pattern enhances code maintainability by separating business logic from side effects, making 85% of code pure functions. Magnar also shares insights on the importance of Datomic for data management and practical strategies for implementing FC/IS. The discussion touches on the real-world benefits, including improved error handling and REPL-driven development, along with challenges in transitioning to this modern architecture.