This deliverable is the second and final release of the EOSC Service Architecture. It sets the foundations characterising the EOSC System:(i) Its functionalities are provisioned as-a-Service; (ii) It is a highly distributed, evolving and heterogeneous hybrid cloud; (iii)Its operation and development is regulated by a set of Rules of Participation; (iv) It is modelled as an open and evolving System of Systems (SoS) where the component systems providing services include existing and emerging Research Infrastructures (including e-Infrastructures) and other types of Service Providers; (v) EOSC services provision is based on an open and evolving set of EOSC Nodes spread across several organisations and regions; (vi) EOSC Services should promote and support FAIRness. The deliverable identifies 47 classes of services that can be considered at this stage of development as the “Minimal Viable Product” able to match the EOSC overall goal. Such services include cross-cutting services together with services specifically envisaged to serve researchers, research administrators, third-party service providers as well as EOSC managers, service providers and service suppliers. This deliverable briefly highlights major contextual aspects already introduced in D5.1 and then describes the identified classes of services. The deliverable also discusses aspects related to “how” the system can/should be developed. The notions of “federation” and “interoperability” related to the building of this EOSC System are addressed highlighting the importance of dealing with these two concepts per-single service rather than from the perspective of EOSC as a whole.