This document summarizes Sergiy's talk on isolated architecture in Ruby. It discusses principles like the Single Responsibility Principle, Dependency Inversion, and separating domains. It emphasizes keeping software simple through composition, modularity, and constant refactoring. Sergiy advocates test-driven development and functional programming techniques like immutable data and pure functions. He outlines layers for a domain-driven design including domain types, application services, infrastructure, UI, and persistence.