The answer is that the query scans too many partitions or data without efficient pruning. This error occurs when BigQuery’s WHERE clause fails to filter on the partitioning column, forcing a full scan across all partitions instead of reading only the relevant slices. Partition pruning is BigQuery’s mechanism to skip unnecessary data by using the partition column in the filter, and when that filter is missing or uses a non-partitioned column, the query processes every partition, hitting cost or quota limits. On the Google Professional Data Engineer exam, this scenario tests your understanding of cost optimization and query performance, often appearing as a trap where a seemingly correct query lacks a partition filter on a large table. A common memory tip is “prune with the partition column”—always verify that your WHERE clause references the table’s partition column to avoid scanning the entire dataset.
PDE Designing data processing systems Practice Question
This PDE practice question tests your understanding of designing data processing systems. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
Exhibit
Refer to the exhibit.
Exhibit:
Error: Resources exceeded during query execution.
Query statement: SELECT *
FROM `project.dataset.table`
WHERE date >= '2023-01-01'
A BigQuery query fails with the error shown in the exhibit. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Refer to the exhibit.
Exhibit:
Error: Resources exceeded during query execution.
Query statement: SELECT *
FROM `project.dataset.table`
WHERE date >= '2023-01-01'
A
The query scans too many partitions or data without efficient pruning
SELECT * on a large table can exceed resource limits; partition pruning might help.
B
The table has too many partitions
Why wrong: BigQuery handles thousands of partitions without issue.
C
The user does not have permission to query the table
Why wrong: Permission errors would be access denied, not resource exceeded.
D
Insufficient slot capacity in the project
Why wrong: Slot capacity issues result in a different error about unavailable resources.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The query scans too many partitions or data without efficient pruning
The error indicates that the query attempted to scan too many partitions or a large amount of data without effective partition pruning. BigQuery charges based on the amount of data processed, and queries that scan all partitions of a large table can hit limits or incur high costs. The most likely cause is that the query's WHERE clause does not filter on the partitioning column, forcing a full table scan across all partitions.
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.
✓
The query scans too many partitions or data without efficient pruning
Why this is correct
SELECT * on a large table can exceed resource limits; partition pruning might help.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The table has too many partitions
Why it's wrong here
BigQuery handles thousands of partitions without issue.
✗
The user does not have permission to query the table
Why it's wrong here
Permission errors would be access denied, not resource exceeded.
✗
Insufficient slot capacity in the project
Why it's wrong here
Slot capacity issues result in a different error about unavailable resources.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the distinction between 'too many partitions' (a table design issue) and 'scanning too many partitions' (a query design issue), leading candidates to mistakenly choose the option about partition count rather than the lack of pruning.
Detailed technical explanation
How to think about this question
BigQuery uses columnar storage and partitions tables by a specified column (e.g., date). When a query filters on the partition column, BigQuery prunes partitions, scanning only relevant data. Without such filtering, the query scans all partitions, which can exceed the 400 TB limit per query or trigger a 'Partition scan too large' error. In real-world scenarios, this often happens when analysts forget to include a date range filter on a time-partitioned table, leading to unexpectedly large scans and failures.
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.
TExam Day Tips
→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 startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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: The query scans too many partitions or data without efficient pruning — The error indicates that the query attempted to scan too many partitions or a large amount of data without effective partition pruning. BigQuery charges based on the amount of data processed, and queries that scan all partitions of a large table can hit limits or incur high costs. The most likely cause is that the query's WHERE clause does not filter on the partitioning column, forcing a full table scan across all partitions.
What should I do if I get this PDE question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
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.
Question Discussion
Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.
Sign in to join the discussion.