The Metadata Service can be configured to aggregate metadata from multiple other Metadata Service instances.
The aggregated MDS APIs and scripts copy metadata from one or many metadata services into a single data store. This enables a metadata service to act as a central API for browsing Metadata using clients such as the Ecosystem browser.
The aggregate metadata APIs and migrations are disabled by default unless USE_AGG_MDS=true is specified. The AGG_MDS_NAMESPACE should also be defined for shared Elasticserach environments so that a unique index is used per-instance.
The aggregate cache is built using Elasticsearch. See the docker-compose.yaml file (specifically the aggregate_migration service) for details regarding how aggregate data is populated.
See the Configuring the Gen3 Aggregate Metadata Service and Adapters documentation.