Azure Front Door is Microsoft's content delivery network within Azure, designed to deliver applications' static and dynamic web content quickly and securely worldwide. The service provides global load balancing and failover between origin servers, an integrated web application firewall, bot rules, DDoS protection, a routing rules engine and private access to the origin through Azure Private Link. Azure DNS complements it with hosting and resolution of public and private DNS domains, and Azure Traffic Manager with DNS-based traffic distribution. Everything is a cloud service managed through the portal, APIs and command line.
Microsoft is a US company and is subject to US law such as the CLOUD Act. Front Door is a globally distributed multi-tenant service that runs on edge locations worldwide and is not tied to a single Azure region; you choose only a location for the resource group's metadata. There is no open-source version or self-hosted variant. European organisations should bear in mind that traffic can pass through locations outside the EU and that they depend on a US provider.