Airbnb's migration from a monolithic Ruby on Rails architecture to a service-oriented architecture (SOA) in 2018 was driven by the need for improved maintainability and reduced single points of failure. The company outlined four key lessons learned during this transition: invest in shared infrastructure early, simplify service dependencies, centralize data hydration, and separate UI logic from backend logic. This article discusses the transition and compares Airbnb's architectural choices with those of other tech giants like Meta, Google, and Uber.