Metadata quality is stored by the Hub as DQV measurements in a triple store. Unfortunately, SPARQL is not as fast as would be required for responsive UIs. This is alleviated by the Metrics Cache, which fetches and stores the DQV measurements as documents in a MongoDB. These are grouped by various common concepts which reflects the structure used in the UI and Reporter.
The service is not a pipe module. Updating the measurements can be triggered manually or via cron job. The measurements can be retrieved via dedicated endpoints.