DP-750 Certification Practice Question #86

Question

You are the platform engineer for the Contoso lakehouse on Azure Databricks. Finance has asked you to produce a chargeback report that shows the total DBU consumption attributed to the `cost_center` of `analytics-eu` across all classic compute and serverless jobs over the last 30 days.

You have already enforced a custom cluster tag named `cost_center` through a compute policy, and the tag also propagates to serverless usage through a serverless usage policy. You need to query the appropriate Unity Catalog system table so the report attributes usage to that custom tag.

Which query returns the correct chargeback figure?

```sql
-- Option A
SELECT sku_name, usage_unit, SUM(usage_quantity) AS usage
FROM system.billing.usage
WHERE custom_tags['cost_center'] = 'analytics-eu'
  AND usage_date >= current_date() - INTERVAL 30 DAYS
GROUP BY sku_name, usage_unit;
```

```sql
-- Option B
SELECT SUM(usage_quantity) AS usage
FROM system.compute.clusters
WHERE tags['cost_center'] = 'analytics-eu';
```

```sql
-- Option C
SELECT SUM(EstimatedCost) AS usage
FROM system.access.audit
WHERE ServiceName = 'clusters'
  AND cost_center = 'analytics-eu';
```

```sql
-- Option D
SELECT SUM(usage_quantity) AS usage
FROM system.billing.list_prices
WHERE custom_tags['cost_center'] = 'analytics-eu';
```

Accepted Answer

The single source of truth for billable DBU consumption is `system.billing.usage`. Each row carries a `custom_tags` map that includes tags propagated from compute policies (classic compute) and serverless usage policies (serverless jobs), so filtering `custom_tags['cost_center'] = 'analytics-eu'` and summing `usage_quantity` over the last 30 days returns the correct chargeback number. The other system tables either describe inventory (`compute.clusters`), audit events (`access.audit`), or pricing (`billing.list_prices`) and cannot produce a DBU-consumption total attributed to a tag.

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