Sovereign Cloud Stack

One platform — standardized, built and operated by many.

About Sovereign Cloud Stack

Sovereign Cloud Stack (SCS) is a network of existing and future providers of standardized sovereign cloud and container infrastructure to join forces in defining, implementing and operating a fully open, federated, compatible platform. By joining forces, the platform can support a healthy ecosystem for service and application developers and strengthen the digitalization efforts in Europe without creating large risks to lose control over the technology and the data.


Certifiable Standards

We aim to define well-defined standards, that are precise enough so that software implemented and tested on one SCS implementation will work without additional effort on other SCS based infrastructure. The standards are a collection of upstream standards enhanced with specific choices that are not specified upstream. We are working on providing conformance tests so that changes can be validated w.r.t. their impact on compliance.

Certifiable standards are the prerequisite to create a vivid ecosystem on top of SCS.

We also work on (optional) standards with operational topics; transparency with respect to monitoring and root cause analyses in case of issues are immediate customer benefits; for operators, it helps to share knowledge on the Ops piece of DevOps for efficiency and for helping with recruiting staff.

Quality and Security tests are also part of the testing, so conformance with e.g. security standards can also be continuously assured.

Openness and Transparency

All software is fully open source – we don’t believe in open core models. It’s not just the software license: The software is developed in an open development process with open design discussions and decisions by an open community. This ensures that the software really can be used and influenced by the recipients, thus ensuring the freedom of its consumers.

The transparency of the code and the development process is an important ingredient to ensure that the code can be trusted.


The IT world is fast-paced. New technologies replace older ones very quickly. With Sovereign Cloud Stack, we aim to have fairly stable software infrastructure at the base layer, while accommodating rapid change at higher layers. Having a fairly sustainable base layer in place avoids the need for operators to constantly rebuild the base layers.

This also creates the space to work on sustainability with respect to energy consumption: Automating energy-aware placement decisions and using power saving technologies are important topics in SCS.


Our vision replaces centralized infrastructure control with a network of providers that collaborate. The highly compatible SCS clouds, good network connections plus federable identity and access management brings us a significant step closer to create a large global virtual cloud without a central controlling entity.

Advantages …

… for DevOps teams (developing PaaS/SaaS)

Having a well-defined environment that can be operated as small private cloud or as large public clouds alike avoids duplicated implementation and validation work. Targeting SCS is thus rather efficient.

… for Public Cloud Operators

Adhering to SCS standards and being part of the SCS ecosystem creates a much larger set of applications DevOps teams and applications that work on the cloud. The addressable market thus grows significantly.

Moving from only adhering to standards towards using some or all of the SCS modules from the reference implementation also saves a lot of duplicated work in curating, configuring, integrating, automating, testing, documenting the software and building up the operational processes, monitoring, updating, … for running it.

Last not least, the operational work can more easily be shared with others or even outsourced. And skilled staff is more likely to be available.

… for the society

Using modern IT infrastructure with full automation for infrastructure deployment and life cycle management (= Infrastructure as Code) provides a huge boost to the productivity of software DevOps teams. Europe urgently needs this boost to avoid falling (further) behind in the global competition, where more and more traditional industries are disrupted by digital innovation.

Unfortunately, just relying on the hyperscalers comes with many disadvantages:

All of these are inhibitors to adopting hyperscaler clouds.

Having the choice to use local SCS cloud providers or even creating and operating your own SCS cloud gives you the advantages of modern IaC infrastructure without these downsides.

From a geopolitical angle, ensuring that a growing part of the value creation of the increasingly digital value chains can remain in Europe is reducing the strategic risks and is increasing the captured value.

Deployment models

Standard SCS is optimized for small (half a rack) to large (hundreds of servers per region) clouds in the data center or the near edge.

The deployment can be done as a private cloud by a skilled IT department or as a public cloud by a CSP. We have both in our network.

We are working on planning optimized far-edge scenarios in a followup project (“SCS-2”).

Sovereign Cloud Stack and Gaia-X

Digital sovereignty is a key goal of Gaia-X. We believe that many scenarios that require sovereignty at the data level can not be achieved well without control over the infrastructure.

SCS thus intends to make it a lot easier to provide sovereign infrastructure. As such it has been included in the Gaia-X effort. Historically, it was a sub working group in the software and architecture working group in workstream 2 – it is today an (Open) Work Package connected to the Provider Working Group of the Technical Committee of the Gaia-X AISBL.

SCS members support many efforts in Gaia-X, such as the Federation Services / Open Source Software Working Group, the Infrastructure sub working group, the Architecture of Standards work package, the product and service board, the minimal viable gaia piloting group, the self-descriptions work package and the cross-environment service orchestration group.

There is a close link with the Gaia-X Federation Services (gxfs) effort. There is a shared vision of providing SCS with GXFS on top as a platform for sovereign data services. SCS partners support GXFS with infrastructure to validate the gxfs implementation.

Project and funding

The SCS project was initiated by volunteers. With the funding, the project is now hosted by the OSB alliance which has hired a small central team to drive and coordinate the projects.

There is a growing community of volunteers around the central team that contributes to the SCS project.

With the funding in place, FOSS development that does not necessarily benefit individual companies enough can also be funded. The work packages / lots for this go through an open tender process.

Technological Vision

Automating the life cycle management of all components is key: Basic infrastructure services such as the database, message queue, …, the operational stack (monitoring, patching, logging, metering, …), the identity management stack (LDAP, keycloak, …), the base virtualization layer (KVM, ceph, OVN), the VM layer (OpenStack core services) and the Kubernetes tooling are all covered by this. We use a containerized deployment driven by Ansible. The containers at the base layer however are managed using classical Docker/Podman – we explicitly control placement etc. here and do not see the highly dynamic capabilities of Kubernetes at this layer as an advantage. This is of course different in higher layers that change much more often depending on the customer needs.

The figure shows the architectural structure and components of SCS.

The core OpenStack services are mainly used to be a strong multitenant foundation for managing many k8s clusters – the real service here is k8s aaS – we are offering the k8s cluster API as interface to manage k8s clusters; providers can of course use it internally as well to create managed services. Exposing the OpenStack layer is optional from an SCS standardization point of view. If it is exposed, we however have standards to cover it, so we can deliver compatibility at this layer as well.

The above figure shows an ecosystem with four clouds, two of them using SCS standards. The container layer can be managed across both of them. For cross-cloud container management across other technologies, software like Gardener can be used – we do validate that it functions well on SCS. The picture has been created while working with Acatech on the whitepaper on digital sovereignty. The first edition contains an older version of the picture though.

Note that the technology choices that are not part of the mandatory standard (S) may not necessarily be final. The SCS Platform Services are not part of the base SCS project (“SCS-1”); however we have plans prepared to extend SCS into this space “SCS-3”.

Use SCS and join us

See the page Use SCS.