Is this GDPR or Right to Be Forgotten?
In recent weeks I've seen quite a lot of people pointing out that "data necessary to provide the service" is exempt from GDPR. A reliable backup system is *definitely* fairly and squarely in that category, particularly if there are legal consequences to delivering wrong answers. So I can see no GDPR angle on this.
As for the right to be forgotten, well, IANAL but wasn't all this discussed at length some weeks or months ago?