Wow Padriac, that makes me think what Robert C. Martin (aka Uncle Bob) always say: start with the simplest version that you need, even without database, and then scale as it is required. If I am not wrong he explains the case about the Database in his cleancoders course about TDD. Basically, when he and his team was hired to develop a wiki like a 20 years ago, they used TDD. The customer said that wanted a database, and they passed. They did all the hard development (the conversion from text to HTML, and later the service) without any database, and when they finished, they solved the persistence with a file system. They didn't need anything else.

I love this conversations. Thanks!