In DBR 16.1+ Databricks switched the BigQuery federation connector from JDBC to the BigQuery Storage API,
which parallelizes reads (more jobs) and transfers data directly from BigQuery to Databricks compute—so cross‑cloud queries (Azure → GCP) can incur BigQuery Storage API egress charges; maximize pushdown (filters, projections, limits, joins), reduce selected columns, and consider co‑locating compute (Databricks on GCP) to mitigate network costs.