Federated repositories employ a topology with two separate but integrated mechanisms, whereby artifact metadata is replicated continuously but separately from the binary content. This is done to enable fast synchronization of the metadata, which is replicated rapidly in bulk, while the binary content is brought asynchronously using a separate mechanism based on workers. Priority can always be given to specific binaries on user demand as required.
Having the metadata replicated quickly is critical because file properties cannot be uploaded before the file itself is uploaded. This is especially true when working with Docker manifests, which cannot be uploaded before the layers listed in the manifest are uploaded.
Dividing the federation of the metadata and the binaries into two separate mechanisms also provides a solution with excellent scalability.