- A
Add a random prefix to the row key (e.g., hash of deviceID modulo 1000)
Hashing the device ID distributes writes across tablet servers, reducing hotspots.
- B
Reverse the key to 'timestamp#deviceID'
Why wrong: This would cause all writes to go to the same tablet for the current timestamp, worsening hotspots.
- C
Use a single column family with many columns
Why wrong: Column families don't affect row key distribution.
- D
Store all data in one row per device
Why wrong: Storing all data in one row would cause excessive I/O and contention.
Question 643 of 1,000
PDE Storing the Data Practice Question
This PDE practice question tests your understanding of storing 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.
An IoT application writes sensor readings to Cloud Bigtable with a row key of 'deviceID#timestamp'. The team notices high write latency and hotspots on a few nodes. Which row key design change would most likely improve performance?
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
✓
Add a random prefix to the row key (e.g., hash of deviceID modulo 1000)
Prefixing timestamps can cause hotspots because writes go to the same tablet server for the same time range. Hashing the device ID or using a field-leveled design (e.g., deviceID inverted) distributes writes across nodes. Adding a random prefix helps but salting with a hash is more systematic.
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.
- ✓
Add a random prefix to the row key (e.g., hash of deviceID modulo 1000)
Why this is correct
Hashing the device ID distributes writes across tablet servers, reducing hotspots.
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.
- ✗
Reverse the key to 'timestamp#deviceID'
Why it's wrong here
This would cause all writes to go to the same tablet for the current timestamp, worsening hotspots.
- ✗
Use a single column family with many columns
Why it's wrong here
Column families don't affect row key distribution.
- ✗
Store all data in one row per device
Why it's wrong here
Storing all data in one row would cause excessive I/O and contention.
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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Storing the Data — study guide chapter
Learn the concepts, then practise the questions
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Storing the Data practice questions
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FAQ
Questions learners often ask
What does this PDE question test?
Storing the Data — This question tests Storing the Data — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Add a random prefix to the row key (e.g., hash of deviceID modulo 1000) — Prefixing timestamps can cause hotspots because writes go to the same tablet server for the same time range. Hashing the device ID or using a field-leveled design (e.g., deviceID inverted) distributes writes across nodes. Adding a random prefix helps but salting with a hash is more systematic.
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: "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: 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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