- A
Legacy streaming inserts
Why wrong: Legacy streaming inserts have a 1 MB limit per row and higher latency, and are being deprecated.
- B
Pending mode
Why wrong: Pending mode is for writing data that is not immediately visible; it is used for batch loads, not real-time.
- C
Buffered mode
Buffered mode provides low-latency streaming with data available within seconds, and is cost-effective for high-volume ingestion.
- D
Committed mode
Why wrong: Committed mode writes data directly to BigQuery storage with strong durability, but at higher cost and latency than buffered mode.
Question 680 of 1,000
PDE Ingesting and Processing the Data Practice Question
This PDE practice question tests your understanding of ingesting and processing the data. 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.
A financial services company needs to ingest real-time trade data from multiple sources into BigQuery for immediate fraud detection. The data volume is high (1 million messages per second) and each message must be available for queries within seconds. They are considering the Storage Write API. Which stream mode should they choose to balance data availability and cost?
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
✓
Buffered mode
Buffered mode (option C) is correct because it provides the best balance between data availability and cost for high-volume, real-time fraud detection. In buffered mode, data is written to BigQuery's managed storage within seconds, making it available for queries almost immediately, while the cost is lower than committed mode because buffered mode does not require an additional commit step. This mode is ideal for streaming use cases where latency is critical but cost efficiency is also a priority.
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.
- ✗
Legacy streaming inserts
Why it's wrong here
Legacy streaming inserts have a 1 MB limit per row and higher latency, and are being deprecated.
- ✗
Pending mode
Why it's wrong here
Pending mode is for writing data that is not immediately visible; it is used for batch loads, not real-time.
- ✓
Buffered mode
Why this is correct
Buffered mode provides low-latency streaming with data available within seconds, and is cost-effective for high-volume ingestion.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Committed mode
Why it's wrong here
Committed mode writes data directly to BigQuery storage with strong durability, but at higher cost and latency than buffered mode.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Candidates often mistakenly think committed mode provides the best data availability, but for this Google BigQuery scenario, buffered mode offers the right balance of near-real-time availability and cost efficiency.
Detailed technical explanation
How to think about this question
The Storage Write API uses a gRPC-based protocol that supports multiple stream modes, each with different trade-offs in latency, cost, and consistency. Buffered mode leverages an internal buffer that automatically commits data within seconds, providing a sweet spot for real-time analytics. In contrast, committed mode requires an explicit commit RPC, which adds overhead and cost, while pending mode is designed for transactional workflows where data must be staged before finalization.
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.
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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: Buffered mode — Buffered mode (option C) is correct because it provides the best balance between data availability and cost for high-volume, real-time fraud detection. In buffered mode, data is written to BigQuery's managed storage within seconds, making it available for queries almost immediately, while the cost is lower than committed mode because buffered mode does not require an additional commit step. This mode is ideal for streaming use cases where latency is critical but cost efficiency is also a priority.
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.
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Last reviewed: Jul 4, 2026
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