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PCDE Practice Question: Design innovative, scalable, and highly available cloud database solutions
An organization is designing a Cloud Spanner schema for a social media application. The application frequently queries for all posts by a specific user, and also updates the number of likes on a post. To ensure high performance and avoid hotspots, which TWO schema design principles should the team apply? (Choose two.)
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
✓
Interleave the Post table under the User table using UserID as the first part of the primary key
Interleaving the Post table under the User table colocates posts with their user, making queries for a user's posts efficient by reducing distributed reads. Using a UUID for the post ID ensures writes are distributed across the cluster, avoiding hotspots from sequential keys like timestamps.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Interleave the Post table under the User table using UserID as the first part of the primary key
Why this is correct
Interleaving provides data locality for user-post queries.
- ✗
Use a secondary index on the Post table for UserID queries
Why it's wrong here
A secondary index is less efficient than interleaving for this pattern.
- ✗
Denormalize the like count into the User table to avoid joins
Why it's wrong here
Denormalization leads to update anomalies and increased write amplification.
- ✗
Use a monotonically increasing integer as the post ID to simplify indexing
Why it's wrong here
Monotonically increasing keys cause write hotspots.
- ✓
Use a UUID as the post ID to distribute writes evenly
Why this is correct
UUIDs are random and spread write load across nodes.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.