When deciding how and when to reuse code, there are many tradeoffs to consider, each with varying degrees of consistency and indirection.

Modern applications increasingly interface with lots of external systems — third-party APIs, databases, message queues, etc. In some cases, we may have control over the shape of the data being transmitted, but in other cases we may be at the mercy of something else. If we're not careful, implementation details like the shape of the data and the naming of the fields can permeate throughout our code.