Entity getOwner()

In what table does an entity “foo” get its metadata stored? In Drupal 7, there are tables for all the fields for a content type and the node table had some metadata stored, but most data for a content type were in other tables. I think I understand that configuration is what metadata is required for an entity. But I cannot figure out which tables would store an association between node/100 and user/10. Using breakpoints I’m trying to troubleshoot where in the node object this info resides and try to deduce its definitions to backtrack where metadata like author/owner is stored.