- A
Create a materialized view that pre-aggregates data by user_id and date
Why wrong: Materialized views can improve query performance but do not address the root cause of scanning too many partitions. They also incur additional storage costs.
- B
Remove partitioning and rely solely on clustering
Why wrong: Without partitioning, queries would scan the entire table, which is worse for time-range queries.
- C
Change the partition column to a DATE column based on event_timestamp and keep clustering on user_id
If the ingestion time does not match the event timestamp, queries filtering on event time will not prune partitions effectively. Partitioning on the actual event date ensures partition pruning aligns with query filters.
- D
Add clustering on a second column like event_type
Why wrong: Adding another clustering column may not help if the partition pruning is the main issue. Clustering improves within-partition filtering but does not reduce the number of partitions scanned.
PDE Designing Data Processing Systems Practice Question
This PDE practice question tests your understanding of designing data processing systems. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
You have a BigQuery table that is partitioned by ingestion time and clustered on user_id. The table stores event logs and is queried frequently by user_id to analyze user behavior over the last 30 days. Queries are still scanning too many partitions. Which optimization should you apply first?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"first"Why it matters: Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
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
Change the partition column to a DATE column based on event_timestamp and keep clustering on user_id
The query filter on user_id already uses clustering, which prunes blocks within a partition. But the query also filters on a date range, which should leverage partition pruning. If queries still scan many partitions, the most likely cause is that the partition filter is not applied effectively. Using a range filter on the partition column (_PARTITIONDATE) or a column used for partitioning will limit partitions scanned. But the question already says the table is partitioned by ingestion time. The best next step is to ensure the query uses a filter on the partition column. However, among the options, changing the partition type to a specific date column (e.g., event_timestamp) with clustering on user_id could improve if the ingestion time doesn't align with the query time range.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Create a materialized view that pre-aggregates data by user_id and date
Why it's wrong here
Materialized views can improve query performance but do not address the root cause of scanning too many partitions. They also incur additional storage costs.
- ✗
Remove partitioning and rely solely on clustering
Why it's wrong here
Without partitioning, queries would scan the entire table, which is worse for time-range queries.
- ✓
Change the partition column to a DATE column based on event_timestamp and keep clustering on user_id
Why this is correct
If the ingestion time does not match the event timestamp, queries filtering on event time will not prune partitions effectively. Partitioning on the actual event date ensures partition pruning aligns with query filters.
Clue confirmation
The clue word "first" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Add clustering on a second column like event_type
Why it's wrong here
Adding another clustering column may not help if the partition pruning is the main issue. Clustering improves within-partition filtering but does not reduce the number of partitions scanned.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
- Use explanations to understand the rule behind the answer.
TExam Day Tips
- Underline the problem statement mentally.
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
What to study next
Got this wrong? Here's your next step.
Identify which PDE exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
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Designing Data Processing Systems — study guide chapter
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FAQ
Questions learners often ask
What does this PDE question test?
Designing Data Processing Systems — This question tests Designing Data Processing Systems — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Change the partition column to a DATE column based on event_timestamp and keep clustering on user_id — The query filter on user_id already uses clustering, which prunes blocks within a partition. But the query also filters on a date range, which should leverage partition pruning. If queries still scan many partitions, the most likely cause is that the partition filter is not applied effectively. Using a range filter on the partition column (_PARTITIONDATE) or a column used for partitioning will limit partitions scanned. But the question already says the table is partitioned by ingestion time. The best next step is to ensure the query uses a filter on the partition column. However, among the options, changing the partition type to a specific date column (e.g., event_timestamp) with clustering on user_id could improve if the ingestion time doesn't align with the query time range.
What should I do if I get this PDE question wrong?
Identify which PDE exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Are there clue words in this question I should notice?
Yes — watch for: "first". Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
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Last reviewed: Jul 4, 2026
This PDE practice question is part of Courseiva's free Google Cloud certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the PDE exam.
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