Every application has some real-world thing it is about — an order, a patient, a song — and every database forces you to write that thing down in a particular shape. The shape is the data model, and picking one is the most consequential decision in the project, because it silently decides which future features are a morning’s work and which are a rewrite.
This module walks the three shapes worth knowing — documents, relations, and graphs — and the question that actually chooses between them, which is not “which database is fastest” but “what do the relationships in my data look like, and which way do the queries run across them?”
Along the way, query languages: why saying what you want beats saying how to get it in almost every case, and what you give up in the rare cases where it doesn’t.