Question 644 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 team is designing a schema for Cloud Spanner to store user profiles. The primary access pattern is to read a user's profile by their unique user ID. To avoid write hotspots, which primary key design strategy should the team 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
✓
Use a UUID (universally unique identifier) as the primary key
Monotonically increasing keys (e.g., sequential integers or timestamps) cause all writes to hit the same tablet, creating hotspots. Using a random UUID distributes writes evenly across the cluster, avoiding hotspots.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Use the user's email address as the primary key
Why it's wrong here
Email addresses may be concentrated (e.g., same domain) leading to hotspots, and they are not guaranteed to be unique.
- ✗
Use a monotonically increasing integer as the primary key
Why it's wrong here
Monotonically increasing keys cause hotspots as all writes go to the same tablet.
- ✓
Use a UUID (universally unique identifier) as the primary key
Why this is correct
UUIDs are randomly distributed, spreading writes across tablets and avoiding hotspots.
- ✗
Use a timestamp as the primary key
Why it's wrong here
Timestamps are monotonically increasing and cause write hotspots.
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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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