- A
The data was stored in the streaming buffer for more than 24 hours, and BigQuery automatically flushes it to the table.
Why wrong: A is wrong because the streaming buffer maximum latency is 90 minutes, not 24 hours.
- B
BigQuery time travel allows querying data from the past, including data still in the streaming buffer.
Why wrong: D is wrong because time travel applies to committed data, not to the streaming buffer.
- C
The table has an expiration set, and the data is made visible as soon as the table is about to expire.
Why wrong: B is wrong because table expiration does not affect streaming buffer visibility.
- D
The streaming buffer reached its maximum capacity (default 90 minutes) and automatically flushed the data to the table.
C is correct because the streaming buffer flushes data approximately every 90 minutes, making it visible.
Quick Answer
The answer is that the streaming buffer reached its maximum capacity and automatically flushed the data to the table. BigQuery’s streaming buffer is designed to hold recently streamed data for near-real-time querying, but it has a default capacity limit of approximately 90 minutes. Once that limit is hit—meaning the buffer is full—BigQuery performs an automatic flush, writing the buffered rows to the table’s storage and making them immediately visible, even if they were streamed only minutes earlier. On the Google Professional Data Engineer exam, this scenario tests your understanding of streaming buffer behavior versus manual flushing or table expiration. A common trap is assuming that data only becomes visible after a manual query or a forced flush, but the auto-flush mechanism is triggered by capacity. To remember this, think of the buffer as a bucket: when it overflows after 90 minutes, the data spills into the table automatically.
PDE Practice Question: Building and operationalizing data processing systems
This PDE practice question tests your understanding of building and operationalizing 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.
A company uses BigQuery for real-time analytics. They stream data from IoT devices into a BigQuery table. After a few hours, some of the recent data becomes visible in the table although it was streamed less than 10 minutes ago. The data team confirms that no one ran any manual queries. What is the most likely reason for the data visibility?
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.
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
The streaming buffer reached its maximum capacity (default 90 minutes) and automatically flushed the data to the table.
Option D is correct because BigQuery's streaming buffer has a maximum capacity limit, typically around 90 minutes. When the buffer reaches this capacity, BigQuery automatically flushes the buffered data to the table, making it visible. This explains why data streamed less than 10 minutes ago became visible after a few hours.
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 data was stored in the streaming buffer for more than 24 hours, and BigQuery automatically flushes it to the table.
Why it's wrong here
A is wrong because the streaming buffer maximum latency is 90 minutes, not 24 hours.
- ✗
BigQuery time travel allows querying data from the past, including data still in the streaming buffer.
Why it's wrong here
D is wrong because time travel applies to committed data, not to the streaming buffer.
- ✗
The table has an expiration set, and the data is made visible as soon as the table is about to expire.
Why it's wrong here
B is wrong because table expiration does not affect streaming buffer visibility.
- ✓
The streaming buffer reached its maximum capacity (default 90 minutes) and automatically flushed the data to the table.
Why this is correct
C is correct because the streaming buffer flushes data approximately every 90 minutes, making it visible.
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.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often assume streaming data is immediately visible or that time travel is responsible for visibility, but BigQuery's streaming buffer has a finite capacity that triggers automatic flushes, making data visible after a delay.
Detailed technical explanation
How to think about this question
BigQuery's streaming buffer is an in-memory, write-optimized store that holds recently streamed data for up to approximately 90 minutes before being committed to the table's storage. The flush is triggered either by reaching a size or time threshold, ensuring data durability and eventual consistency. In real-world scenarios, high-volume IoT streams can fill the buffer quickly, causing early flushes and making data visible sooner than the default 90-minute window.
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 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 exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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FAQ
Questions learners often ask
What does this PDE question test?
Building and operationalizing data processing systems — This question tests Building and operationalizing 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 streaming buffer reached its maximum capacity (default 90 minutes) and automatically flushed the data to the table. — Option D is correct because BigQuery's streaming buffer has a maximum capacity limit, typically around 90 minutes. When the buffer reaches this capacity, BigQuery automatically flushes the buffered data to the table, making it visible. This explains why data streamed less than 10 minutes ago became visible after a few hours.
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
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Last reviewed: Jun 24, 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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