- A
Fixed windows of 1 hour with allowed lateness of 2 hours and trigger every 5 minutes (early) and on watermark (late) with accumulating fired panes
Fixed windows match the hourly aggregation requirement. Allowed lateness of 2 hours handles late data. Early triggers provide near-real-time results. Accumulating fired panes ensures updates are included.
- B
Global window with triggers every 5 minutes
Why wrong: Global window does not provide hourly boundaries; it would aggregate all data together, not by hour.
- C
Sliding windows of 1 hour with 30-minute offset
Why wrong: Sliding windows create overlapping windows, which is not what is needed for distinct hourly aggregations.
- D
Session windows with 10-minute gap duration
Why wrong: Session windows group events based on inactivity gaps, not fixed hourly intervals.
PDE Designing Data Processing Systems Practice Question
This PDE practice question tests your understanding of designing data processing systems. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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.
You are designing a data pipeline that processes streaming events with late-arriving data (up to 2 hours late). The pipeline must compute hourly aggregations and emit results as soon as possible, but must also accurately update results when late data arrives. You want to minimize overall processing cost. Which Dataflow windowing and trigger configuration should you use?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"minimum / minimize"Why it matters: Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
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
Fixed windows of 1 hour with allowed lateness of 2 hours and trigger every 5 minutes (early) and on watermark (late) with accumulating fired panes
Session windows are ideal for capturing bursts of user activity but not for fixed hourly aggregations. The best approach is to use fixed windows with allowed lateness of 2 hours and triggering early every N minutes (e.g., 5 minutes) and also on watermark advancement. This provides early results while allowing late data to update the window. Using accumulating and discarding late panes (or just accumulating) depends on the use case; but here, accumulating fired panes is typical for correctness.
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.
- ✓
Fixed windows of 1 hour with allowed lateness of 2 hours and trigger every 5 minutes (early) and on watermark (late) with accumulating fired panes
Why this is correct
Fixed windows match the hourly aggregation requirement. Allowed lateness of 2 hours handles late data. Early triggers provide near-real-time results. Accumulating fired panes ensures updates are included.
Clue confirmation
The clue word "minimum / minimize" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Global window with triggers every 5 minutes
Why it's wrong here
Global window does not provide hourly boundaries; it would aggregate all data together, not by hour.
- ✗
Sliding windows of 1 hour with 30-minute offset
Why it's wrong here
Sliding windows create overlapping windows, which is not what is needed for distinct hourly aggregations.
- ✗
Session windows with 10-minute gap duration
Why it's wrong here
Session windows group events based on inactivity gaps, not fixed hourly intervals.
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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Designing Data Processing Systems — study guide chapter
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FAQ
Questions learners often ask
What does this PDE question test?
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: Fixed windows of 1 hour with allowed lateness of 2 hours and trigger every 5 minutes (early) and on watermark (late) with accumulating fired panes — Session windows are ideal for capturing bursts of user activity but not for fixed hourly aggregations. The best approach is to use fixed windows with allowed lateness of 2 hours and triggering early every N minutes (e.g., 5 minutes) and also on watermark advancement. This provides early results while allowing late data to update the window. Using accumulating and discarding late panes (or just accumulating) depends on the use case; but here, accumulating fired panes is typical for correctness.
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.
Are there clue words in this question I should notice?
Yes — watch for: "minimum / minimize". Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
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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