I think the spirit of the article is: you should be able to "download real data from yesterday until now", and be able to run the system locally (or in a stage

I think the spirit of the article is: you should be able to "download real data from yesterday until now", and be able to run the system locally (or in a stage server wherever). Sure, with some mocks or not, but that's super convenient for testing, debugging, etc. without having to risk nasty "write tests" in production