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Design innovative, scalable, and highly available cloud database solutions →hardMultiple ChoiceObjective-mapped
PCDE Practice Question: Design innovative, scalable, and highly available cloud database solutions
An engineer is designing a Cloud Spanner table for a global user activity tracking system with high write throughput. Which primary key design is BEST to avoid hotspots?
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
✓
UUID string (generated by application)
Using a UUID or hash-prefixed key distributes writes evenly across nodes, preventing hotspots that occur with monotonically increasing keys.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Monotonically increasing integer (INT64) with auto-increment
Why it's wrong here
Monotonically increasing keys cause write hotspots on the last tablet.
- ✗
Composite key with user_id as first part
Why it's wrong here
If user_id is sequential, it may still cause hotspots; UUID is better.
- ✓
UUID string (generated by application)
Why this is correct
UUIDs are randomly distributed, avoiding write hotspots.
- ✗
Timestamp as primary key
Why it's wrong here
Timestamps are monotonically increasing, causing 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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