This nugget from Jacob Kaplan-Moss is a bit old, and from a Django-centric perspective, but captures what’s been tripping me up with Python web app frameworks and building RESTful APIs:
Conflating models and resources
In the REST world, the resource is key, and it’s really tempting to simply look at a Django model and make a direct link between resources and models — one model, one resource. This fails, though, as soon as you need to provide any sort of aggregated resource, and it really fails with highly denormalized models. Think about a Superhero model: a single
GET /heros/superman/ought to return all his vital stats along with a list of related Power objects, a list of his related Friend objects, etc. So the data associated with a resource might actually come out of a bunch of models. Thinkselect_related(), except arbitrary.