The backend uses sequelize to query a Postgres database.
This database's schema is automatically generated in ./scr/model/ using sequelize-auto. In case the backend schema changes, one can regenerate these files by running gulp build-models. Be careful, regenerating the models might prevent the backend from building (which is of course intentional since this failure would most likely come from a typing error in the code).
More generally, running gulp clean && gulp build will build everything you need from the server.