- A
Interleave the Post table within the User table.
Interleaving optimizes parent-child queries.
- B
Create a secondary index on PostId.
Why wrong: This helps lookups by PostId, not by user.
- C
Use a monotonically increasing integer for PostId.
Why wrong: Monotonically increasing keys can cause hotspots in Spanner.
- D
Use a UUID for PostId.
Why wrong: UUID distributes writes but does not improve query performance for user posts.
- E
Use (UserId, PostTimestamp) as the primary key of the Post table.
This allows efficient range scans by user and timestamp.
Question 978 of 1,000
PCDOE Design and Plan Database Solutions Practice Question
This PCDOE practice question tests your understanding of design and plan database solutions. 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 engineer is designing a Cloud Spanner schema for a social media application. The database will have a User table and a Post table. Users have many posts, and the application frequently queries all posts for a user, ordered by timestamp. Which two schema design choices will improve performance? (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 within the User table.
Option A is correct because interleaving the Post table within the User table physically co-locates rows for a user and their posts on the same split, enabling fast, low-latency queries for all posts by a user. This design avoids cross-node lookups and leverages Cloud Spanner's hierarchical storage to reduce read overhead.
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.
- ✓
Interleave the Post table within the User table.
Why this is correct
Interleaving optimizes parent-child queries.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Create a secondary index on PostId.
Why it's wrong here
This helps lookups by PostId, not by user.
- ✗
Use a monotonically increasing integer for PostId.
Why it's wrong here
Monotonically increasing keys can cause hotspots in Spanner.
- ✗
Use a UUID for PostId.
Why it's wrong here
UUID distributes writes but does not improve query performance for user posts.
- ✓
Use (UserId, PostTimestamp) as the primary key of the Post table.
Why this is correct
This allows efficient range scans by user and timestamp.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that any index or unique key design is beneficial, but in Cloud Spanner, the physical storage order and interleaving are critical for query performance, not just uniqueness or distribution.
Detailed technical explanation
How to think about this question
Interleaving in Cloud Spanner uses the parent-child table relationship to store child rows physically adjacent to their parent row within the same split, which minimizes the number of splits accessed during a parent-key-based query. The primary key (UserId, PostTimestamp) in option E enables efficient range scans for a specific user's posts in timestamp order without requiring a separate sort operation, as Cloud Spanner stores rows in primary key order.
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.
TExam Day Tips
- 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 media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this PCDOE question test?
Design and Plan Database Solutions — This question tests Design and Plan Database Solutions — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Interleave the Post table within the User table. — Option A is correct because interleaving the Post table within the User table physically co-locates rows for a user and their posts on the same split, enabling fast, low-latency queries for all posts by a user. This design avoids cross-node lookups and leverages Cloud Spanner's hierarchical storage to reduce read overhead.
What should I do if I get this PCDOE question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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 PCDOE 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 PCDOE exam.
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