When Feature Simplicity Masks System Complexity

This post reveals why adding file type support is far more complex than it appears: it requires coordinated changes across API validation, content-type mapping, file extraction, frontend controls, and database constraints. Understanding how these layers must work in concert is crucial for designing systems that can scale features without creating hidden failure modes. It demonstrates a core architectural principle: separation of concerns doesn't mean independence—it means each layer must enforce its part of the contract.