PDE Designing Data Processing Systems Practice Question
A developer wants to create a BigQuery table that automatically expires data older than 30 days to reduce storage costs. Which table design feature should be used?
⚠ Common exam trap
PDE often tests the difference between partitioning, clustering, and expiration features, and candidates may confuse clustering with retention or pick materialized views for cost reduction.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Partitioned table with partition expiration
BigQuery partitioned tables support partition expiration, which automatically deletes partitions older than a specified number of days. Setting a partition expiration of 30 days on a time-partitioned table will drop data older than 30 days, reducing storage costs. This is the native, cost-effective way to enforce data retention.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Authorized view
Why it's wrong here
An authorized view grants query access to a view's underlying dataset without giving direct table permissions; it controls access, not data retention, so no rows expire. It is tempting because it is a governance feature that limits exposure of sensitive data, which is its real purpose.
- ✗
Clustered table
Why it's wrong here
Clustering organises table data into sorted blocks to prune scans and cut query cost; it enforces no age-based deletion, so rows older than 30 days remain stored. It is tempting because it also reduces cost, but through query efficiency rather than storage reclamation, which is what the scenario requires.
- ✗
Materialized view
Why it's wrong here
A materialized view caches query results and refreshes on a schedule; it stores precomputed data but applies no row-expiration policy, so old rows persist in the underlying table. It is tempting because it reduces query cost and latency for repeated aggregations, which is its actual purpose.
- ✓
Partitioned table with partition expiration
Why this is correct
Partition expiration automatically deletes partitions once their partition date passes the specified retention period, so data older than 30 days is removed without manual jobs. This satisfies the automatic expiry requirement while keeping recent data queryable, unlike table-level expiration which drops the entire table.
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Last reviewed September 2026 · checked against the official Google Cloud exam blueprint
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