- A
Sliding windows of 10 minutes with allowed lateness of 30 minutes and accumulating panes
Why wrong: Sliding windows are more appropriate for continuous time-based analysis, not for grouping related events. Accumulating panes would cause duplicates if the late data is processed multiple times.
- B
Global window with allowed lateness of 1 hour and accumulating trigger every 5 minutes
Why wrong: Global window would combine all events into a single window, which is not suitable for grouping by session. Accumulating triggers would produce many duplicate results.
- C
Fixed windows of 1 hour with allowed lateness of 1 hour and no accumulation
Why wrong: Fixed windows would require the late event to fall into a specific window, which might not group related events correctly if they are spread across window boundaries. Allowed lateness with no accumulation would discard late data.
- D
Session windows with a 10-minute gap duration and allowed lateness of 1 hour
Session windows group events that occur within a 10-minute gap. Allowed lateness of 1 hour ensures that late events up to an hour after the watermark advance are still included, minimizing duplicates by capturing them in the correct session.
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.
A company is designing a data pipeline that ingests real-time events from IoT devices and must handle late-arriving data (up to 1 hour late) while minimizing duplicate processing. They plan to use Dataflow with Pub/Sub. Which combination of windowing and trigger settings should they use?
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
Session windows with a 10-minute gap duration and allowed lateness of 1 hour
Session windows naturally group events based on a gap duration, so late events within the gap extend the window. Setting the allowed lateness to 1 hour ensures that late events are still included in the correct session. Using withAllowedLateness(1 hour) allows the watermark to advance and the session to finalize after the gap, but late data within 1 hour will trigger a pane update.
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.
- ✗
Sliding windows of 10 minutes with allowed lateness of 30 minutes and accumulating panes
Why it's wrong here
Sliding windows are more appropriate for continuous time-based analysis, not for grouping related events. Accumulating panes would cause duplicates if the late data is processed multiple times.
- ✗
Global window with allowed lateness of 1 hour and accumulating trigger every 5 minutes
Why it's wrong here
Global window would combine all events into a single window, which is not suitable for grouping by session. Accumulating triggers would produce many duplicate results.
- ✗
Fixed windows of 1 hour with allowed lateness of 1 hour and no accumulation
Why it's wrong here
Fixed windows would require the late event to fall into a specific window, which might not group related events correctly if they are spread across window boundaries. Allowed lateness with no accumulation would discard late data.
- ✓
Session windows with a 10-minute gap duration and allowed lateness of 1 hour
Why this is correct
Session windows group events that occur within a 10-minute gap. Allowed lateness of 1 hour ensures that late events up to an hour after the watermark advance are still included, minimizing duplicates by capturing them in the correct session.
Related concept
Read the scenario before looking for a memorised answer.
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 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 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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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: Session windows with a 10-minute gap duration and allowed lateness of 1 hour — Session windows naturally group events based on a gap duration, so late events within the gap extend the window. Setting the allowed lateness to 1 hour ensures that late events are still included in the correct session. Using withAllowedLateness(1 hour) allows the watermark to advance and the session to finalize after the gap, but late data within 1 hour will trigger a pane update.
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.
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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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