- A
Use interleaved tables where Orders is the parent and OrderItems is an interleaved child table with the same primary key prefix.
Interleaving co-locates child rows with their parent, enabling efficient joins and strong consistency.
- B
Store all data in a single table with nullable columns for order item attributes.
Why wrong: This is poor schema design leading to sparsity and inefficiency.
- C
Denormalize by storing order items as a repeated field in the orders table.
Why wrong: Spanner is a relational database; repeated fields are not supported. Denormalization would break relational integrity.
- D
Create two separate tables with a secondary index on customer_id in the orders table and a secondary index on order_id in the order_items table.
Why wrong: This leads to cross-table lookups and slower queries compared to interleaving.
PDE Storing the Data Practice Question
This PDE practice question tests your understanding of storing the data. 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 e-commerce company uses Cloud Spanner for order processing. They need to query orders by customer ID and retrieve all order items. Which schema design pattern should they use for optimal performance?
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 interleaved tables where Orders is the parent and OrderItems is an interleaved child table with the same primary key prefix.
Interleaved tables in Cloud Spanner physically co-locate parent and child rows on the same split, so querying orders by customer_id and retrieving all order items becomes a single, fast key-range scan without cross-node joins. This design exploits Spanner's hierarchical storage model to minimize latency and maximize throughput for this access pattern.
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.
- ✓
Use interleaved tables where Orders is the parent and OrderItems is an interleaved child table with the same primary key prefix.
Why this is correct
Interleaving co-locates child rows with their parent, enabling efficient joins and strong consistency.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Store all data in a single table with nullable columns for order item attributes.
Why it's wrong here
This is poor schema design leading to sparsity and inefficiency.
- ✗
Denormalize by storing order items as a repeated field in the orders table.
Why it's wrong here
Spanner is a relational database; repeated fields are not supported. Denormalization would break relational integrity.
- ✗
Create two separate tables with a secondary index on customer_id in the orders table and a secondary index on order_id in the order_items table.
Why it's wrong here
This leads to cross-table lookups and slower queries compared to interleaving.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the misconception that secondary indexes alone are sufficient for performance, ignoring that Spanner's distributed architecture makes cross-table joins expensive, whereas interleaving provides physical co-location that avoids network round-trips.
Detailed technical explanation
How to think about this question
Under the hood, Spanner interleaving uses the parent's primary key as the prefix for the child's primary key, ensuring that all child rows for a given parent row are stored contiguously on the same tablet. This eliminates the need for a separate index lookup or join for the common 'get all items for an order' query, and it also enables strong transactional consistency for operations spanning parent and child rows without two-phase commit.
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.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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FAQ
Questions learners often ask
What does this PDE question test?
Storing the Data — This question tests Storing the Data — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use interleaved tables where Orders is the parent and OrderItems is an interleaved child table with the same primary key prefix. — Interleaved tables in Cloud Spanner physically co-locate parent and child rows on the same split, so querying orders by customer_id and retrieving all order items becomes a single, fast key-range scan without cross-node joins. This design exploits Spanner's hierarchical storage model to minimize latency and maximize throughput for this access pattern.
What should I do if I get this PDE 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 PDE 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 PDE exam.
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