North Data is an information service, and as such, is not a purchase processing service.
"Purchase processing, in the sense of the data protection law, only exists in those cases where another entity commissions one entity to process personal data. Commissioning of other types of professional services. When, e.g., data processing is neither the main focus, nor does data processing represent at least one core component [of customer-data]. It then does not constitute commissioned processing in the sense of the data protection law."
(Source: FAQ of the Bavarian State Office for Data Protection Supervision https://www.lda.bayern.de/media/FAQ_Abgrenzung_Auftragsverarbeitung.pdf (German), Additional information in square brackets provided by us)