Question 227 of 1,446
Design innovative, scalable, and highly available cloud database solutions →mediumMultiple ChoiceObjective-mapped
PCDE Practice Question: Design innovative, scalable, and highly available cloud database solutions
A company uses Cloud Bigtable to store time-series data from IoT devices. Each device sends a reading every minute. The row key currently is: device_id + timestamp (e.g., 'device123#2024-01-01T00:00:00Z'). Write throughput is lower than expected. Which row key modification would MOST improve write distribution?
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 hash prefix of the device_id (e.g., hash(device_id) + device_id + timestamp)
Adding a hash prefix (salting) to the row key distributes writes across multiple tablet servers. The current row key starts with device_id, which may cause hotspots if many writes target the same device. A hash prefix ensures uniform distribution.
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 hash prefix of the device_id (e.g., hash(device_id) + device_id + timestamp)
Why this is correct
Salting with a hash prefix spreads row keys across tablets, improving write distribution.
- ✗
Reverse the timestamp: timestamp + device_id
Why it's wrong here
Reversing the timestamp does not distribute writes evenly; writes to the same device still hit the same tablet.
- ✗
Use only device_id as the row key
Why it's wrong here
All reads/writes for a device go to a single row, causing hotspots and exceeding Bigtable's row size limits.
- ✗
Remove the device_id and use only timestamp
Why it's wrong here
Using only timestamp would create a hotspot at the current time.
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Last reviewed: Jul 4, 2026
This PCDE 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 PCDE exam.
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