Comment 3 for bug 1672713

Is this the only place where we have foreign key relationships between the identity backend and something else? If so, maybe this isn't as big of a deal since it's all required for a federated deployment. If you're deploying keystone with federation, you'll need to have a sql backend of some kind to store information required for federation. With the development of shadow users, it is also expected that a separate identity backend (e.g. sql) is available to persist the local (federated) user references.