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.
An online retailer uses BigQuery for analytics. They have a time-series table with 5 billion rows and new data arrives every day. They want to optimize query performance and reduce costs by ensuring that queries scan only the partitions they need. Which table design should they use?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use a table partitioned on the timestamp column.
Partitioning on the timestamp column allows BigQuery to perform partition pruning, so queries with filters on that column only scan the relevant partitions. This directly reduces the amount of data read, lowering both query cost (pay-per-byte) and improving performance. For a 5-billion-row table with daily data arrival, time-unit partitioning is the standard design to meet the stated goals.
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.
✓
Use a table partitioned on the timestamp column.
Why this is correct
Allows queries to scan only relevant time-range partitions.
Related concept
Read the scenario before looking for a memorised answer.
✗
Use a table clustered on the timestamp column.
Why it's wrong here
Clustering organizes data within partitions but does not reduce scanned partitions.
✗
Use a table with no partitioning but use LIMIT in queries.
Why it's wrong here
LIMIT reduces rows returned but not scanned bytes.
✗
Use a table partitioned by ingestion time with a partition expiration.
Why it's wrong here
Effective only if data is queried by ingestion time, not the actual timestamp.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Google Cloud often tests the distinction between partitioning (which prunes data at the storage level) and clustering (which only sorts data within a partition or table), leading candidates to mistakenly believe clustering alone can reduce bytes scanned for time-range queries.
Detailed technical explanation
How to think about this question
BigQuery time-unit partitioning creates separate storage blocks (partitions) for each day, hour, month, or year. When a query includes a filter on the partitioning column, the query planner uses the partition decorator to skip entire storage blocks, dramatically reducing the number of bytes read. A subtle behavior is that if the timestamp column is NULL or out of range, those rows go into the __NULL__ or __UNPARTITIONED__ partition, which can still be scanned if not filtered, so data quality checks are important.
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: Use a table partitioned on the timestamp column. — Partitioning on the timestamp column allows BigQuery to perform partition pruning, so queries with filters on that column only scan the relevant partitions. This directly reduces the amount of data read, lowering both query cost (pay-per-byte) and improving performance. For a 5-billion-row table with daily data arrival, time-unit partitioning is the standard design to meet the stated goals.
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.
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.