Hey @refah_1 ,  Thanks for laying out the steps—you’re very close. Here’s a structured checklist to get GCS working with Unity Catalog and a couple of common gotchas to check.

What’s likely going on

• The region mismatch isn’t the root cause; docs emphasize co-locating the bucket and workspace mainly to avoid egress charges, not as a hard requirement for connectivity.
• If your GCS bucket has Hierarchical Namespace (HNS) enabled, Unity Catalog external locations won’t work. Make sure HNS is disabled on that bucket.
• You must assign the required GCS IAM roles to the Databricks‑generated service account associated with your storage credential. The roles are Storage Legacy Bucket Reader and Storage Object Admin, and they must be granted on the bucket to that service account principal exactly.
• To see or use the external location in Databricks, you also need Unity Catalog privileges:

  • BROWSE to list paths in Catalog Explorer.
  • READ FILES to read files via gs://... paths.

Quick validation steps in Databricks

1. In Catalog Explorer, open your External location and click Test connection (verifies READ/WRITE/PATH EXIST/DELETE). If this fails, the issue is with the storage credential, IAM on the bucket, or the path.
2. Confirm your external location URL points to the correct parent path containing the CSV, for example gs://my-bucket/ or gs://my-bucket/path/. Paths must use only ASCII characters (A–Z, a–z, 0–9, /, _, -).
3. Grant yourself the external location privileges:

   • In Catalog Explorer > External locations > your location > Permissions, grant your user/group:
     • BROWSE (to list) and READ FILES (to read).
4. Verify from a notebook: python display(dbutils.fs.ls('gs://<my-bucket>/')) # or the subfolder that contains the CSV python spark.read.format("csv") \ .option("header", "true") \ .option("inferSchema", "true") \ .load('gs://<my-bucket>/<path-to>/file.csv') \ .display()

Double‑check the GCP side

• Ensure you granted the roles to the exact Databricks‑generated service account that appears when you created the storage credential (looks like an email). Assign: * Storage Legacy Bucket Reader * Storage Object Admin on the bucket where the CSV resides.
• If you want Databricks to configure file events (optional but recommended), add the custom Pub/Sub and storage.buckets.update permissions described in the docs; otherwise skip this for now.

About regions

• Co‑locating the workspace and bucket is recommended to avoid egress charges and reduce latency, but region differences alone aren’t called out as a connection blocker in the docs.

If you still can’t see the file

• Confirm HNS is disabled on the bucket (not supported with UC external locations).
• Recreate the storage credential via Catalog Explorer so Databricks generates the service account, then re‑grant the two roles on the bucket to that service account; retest the external location.
• Make sure you’re accessing with Unity Catalog‑enabled compute and using three‑level namespaces elsewhere (catalog.schema.table) to avoid defaulting to the legacy Hive metastore when creating tables over the data.

Next step ideas for your 43GB CSV

• Read the CSV once and write it to Delta for faster, reliable downstream reads: python df = (spark.read.format("csv") .option("header", "true") .option("inferSchema", "true") .load('gs://<my-bucket>/<path-to>/file.csv')) df.write.format("delta").mode("overwrite").save('gs://<my-bucket>/<path-to>/delta') Then use an external location to govern that Delta path, or register an external table over it.