- A
Use Dataflow to read files from GCS, combine them, and write to BigQuery using the Storage Write API in exactly-once mode
Dataflow can efficiently combine small files and write to BigQuery with exactly-once semantics using the Storage Write API.
- B
Use Cloud Functions to trigger on new files and stream each row via the legacy streaming inserts API
Why wrong: Legacy streaming inserts are at-least-once and cost more per GB; not ideal for batch loading many small files.
- C
Use Storage Transfer Service to copy files to a staging bucket, then run a scheduled query to load them
Why wrong: Storage Transfer Service doesn't load into BigQuery; additional steps are needed.
- D
Use BigQuery batch load jobs with a wildcard URI to load all files directly
Why wrong: Loading many small files directly is inefficient and may hit metadata quotas; also lacks built-in exactly-once across retries.
PDE Ingesting and Processing the Data Practice Question
This PDE practice question tests your understanding of ingesting and processing the data. Compare every option against the stated constraints before choosing — the best answer satisfies all requirements, not just the most obvious one. 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.
A data team wants to load millions of small JSON files (each <1 MB) from GCS into BigQuery daily with the lowest cost and fastest performance. They need exactly-once semantics and the ability to detect new files automatically. Which approach is most suitable?
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
Use Dataflow to read files from GCS, combine them, and write to BigQuery using the Storage Write API in exactly-once mode
BigQuery batch loads from GCS with wildcard URIs and the 'auto detect' option can handle many small files efficiently. However, for many small files, loading them directly may be slow. A better approach is to combine files first. Dataflow with file processing can combine and load with exactly-once. Storage Write API is for streaming, not batch. Transfer Service is for copying data, not loading into BigQuery.
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 Dataflow to read files from GCS, combine them, and write to BigQuery using the Storage Write API in exactly-once mode
Why this is correct
Dataflow can efficiently combine small files and write to BigQuery with exactly-once semantics using the Storage Write API.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Use Cloud Functions to trigger on new files and stream each row via the legacy streaming inserts API
Why it's wrong here
Legacy streaming inserts are at-least-once and cost more per GB; not ideal for batch loading many small files.
- ✗
Use Storage Transfer Service to copy files to a staging bucket, then run a scheduled query to load them
Why it's wrong here
Storage Transfer Service doesn't load into BigQuery; additional steps are needed.
- ✗
Use BigQuery batch load jobs with a wildcard URI to load all files directly
Why it's wrong here
Loading many small files directly is inefficient and may hit metadata quotas; also lacks built-in exactly-once across retries.
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 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 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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Ingesting and Processing the Data — study guide chapter
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FAQ
Questions learners often ask
What does this PDE question test?
Ingesting and Processing the Data — This question tests Ingesting and Processing the Data — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use Dataflow to read files from GCS, combine them, and write to BigQuery using the Storage Write API in exactly-once mode — BigQuery batch loads from GCS with wildcard URIs and the 'auto detect' option can handle many small files efficiently. However, for many small files, loading them directly may be slow. A better approach is to combine files first. Dataflow with file processing can combine and load with exactly-once. Storage Write API is for streaming, not batch. Transfer Service is for copying data, not loading into BigQuery.
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.
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 →
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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