While returning data from the database as an API response, the virtuals/methods available on a mongoose document are unnecessary. Lean option can be set on such queries to return just the data directly from the database. It also improves the overall performance of the API.
Relations are logical links which define how models are connected with each other. A document of a model can be connected to one or more documents of the same or another model.
Loopback models can be extended by adding custom methods to them. A method can be:
Destroy All API (Model.destroyAll()) is, by default, disabled to avoid accidental bulk deletion of data. However, it might be required for developmental purposes.