The phrase “source of truth” has become a popular attempt to simplify distributed systems. It sounds great - there is a single place where data is “true”, so if you need the “true” value of an object, you go there for it. However, the phrase is poorly defined and doesn’t tell what to actually do to simplify your system. What does “truth” mean in a system where data may be located and mutated in multiple places? “Source of truth” tries to approximate “