This bundle is intended to be used with Yucca Orm : https://github.com/rjanot/yucca
fos_user:
db_driver: custom
user_class: Acme\Bundle\AcmeBundle\Entity\YurExtendedUser
service:
user_manager: acme_user.user.manager
More informations on https://github.com/FriendsOfSymfony/FOSUserBundle/blob/ef7ca325929ff102fff521653a2e3b88c7a40361/Resources/doc/custom_storage_layer.md