CoreDNS is a DNS server written in Go. It works as a chain of plugins, each performing one DNS function, for example serving zone files, rewriting queries, exposing Prometheus metrics, signing zones or resolving Kubernetes services. Administrators configure it in a Corefile and can compile a build that contains only the plugins they need. It integrates with Kubernetes for service discovery and with etcd, and has plugins for Azure DNS, Google Cloud DNS and Amazon Route 53. CoreDNS is software that you run yourself, on servers or in clusters; the project does not offer a hosted service.
CoreDNS is open source under the Apache License 2.0 and is a graduated project of the Cloud Native Computing Foundation, part of the Linux Foundation. Development takes place on GitHub. Because you operate it yourself, DNS data stays wherever you deploy it, including within the EU, and no vendor has access to your queries. This gives a European organisation control over hosting and updates, at the price of running and maintaining the service.