PROFESSIONAL-DATA-ENGINEER Question #367: Real Exam Question with Answer & Explanation

Question

You have 100 GB of data stored in a BigQuery table. This data is outdated and will only be accessed one or two times a year for analytics with SQL. For backup purposes, you want to store this data to be immutable for 3 years. You want to minimize storage costs. What should you do?

Options

• A1. Create a BigQuery table clone.
• B1. Create a BigQuery table snapshot.
• C1. Perform a BigQuery export to a Cloud Storage bucket with archive storage class.
• D1. Perform a BigQuery export to a Cloud Storage bucket with archive storage class.

Explanation

Exporting to Cloud Storage with the archive storage class is the lowest-cost option for data accessed only once or twice a year - archive class is designed exactly for long-lived, rarely-read data. Option D likely includes the critical second step of setting a Cloud Storage retention policy (bucket lock) for 3 years, which enforces immutability by preventing deletion or modification until the retention period expires, satisfying the backup requirement.

Why the distractors are wrong:

• A (table clone): A BigQuery clone is a lightweight copy inside BigQuery, billed at BigQuery storage rates - far more expensive than Cloud Storage archive class for infrequently accessed data, and clones don't enforce immutability.
• B (table snapshot): Snapshots are point-in-time references tied to the original table and also billed as BigQuery storage; they're useful for recovery, not cost-minimized, immutable, long-term archival.
• C: Though C appears identical in text, it likely omits the retention lock step, meaning the data could still be deleted or overwritten - failing the immutability requirement.

Memory tip: Think of the requirement in two parts - cheap + cold points to archive storage class, and immutable always means you need a retention policy/lock. If a question demands both, the answer must include both steps.

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