Does Metaflow use PostgreSQL to store both artifact data and metadata?

I don't think so. Artifact data is stored in a datastore backend (local, s3, azure etc). Metadata is handled by a metadata provider (local or service).

artifacts are stored using the content addressable store (s3 etc), but the metadata about the artifacts and flow runs are stored in the metadata service, which uses postgres https://github.com/Netflix/metaflow-service

sorry about that. I thought it used a different DB for the metadata