SQLAlchemy provides a few options for handling “cascaded” deletions – from what I can gather, either the ORM tries to handle cascading itself (i.e., where passive_deletes=False [default] and cascade="{...}, delete" is set in a relationship() definition), or it may be “informed” of a database-side ON DELETE CASCADE configuration by specifying passive_deletes=True, in which the ORM may defer some deletes to the DB.