The document discusses architectural refactoring, which is intentionally changing a system's structure without altering its features. Reasons for refactoring include when technology fails to meet user needs or the team fails to deliver for the organization. Common patterns of refactoring include building a monolith initially for speed but later leveraging distributed caching, clustering servers, eliminating session state, and separating data from static assets. The goal is to trade total complexity for local simplicity over time through refactoring.