- A
Create materialized views for common reports.
Why wrong: Materialized views still reside on the primary and consume resources.
- B
Change all joins to use subqueries.
Why wrong: Subqueries are not inherently more efficient and may not reduce load.
- C
Increase the number of vCPUs on the primary instance.
Why wrong: Scaling up helps but is less cost-effective than using replicas for read offloading.
- D
Use read replicas to offload reporting queries.
Read replicas serve read-only traffic without impacting the primary.
Question 166 of 1,000
PCDE Design and implement database schemas Practice Question
This PCDE practice question tests your understanding of design and implement database schemas. 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 platform uses Cloud SQL for PostgreSQL. They need to run complex reporting queries that join several tables. These queries are slowing down the transactional workload. What should they do?
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 read replicas to offload reporting queries.
Option D is correct because read replicas in Cloud SQL for PostgreSQL allow you to offload read-only queries, such as complex reporting joins, from the primary instance. This separation reduces contention for CPU, memory, and I/O resources, preserving transactional performance. Read replicas are asynchronous and can handle heavy analytical workloads without impacting the primary's write path.
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.
- ✗
Create materialized views for common reports.
Why it's wrong here
Materialized views still reside on the primary and consume resources.
- ✗
Change all joins to use subqueries.
Why it's wrong here
Subqueries are not inherently more efficient and may not reduce load.
- ✗
Increase the number of vCPUs on the primary instance.
Why it's wrong here
Scaling up helps but is less cost-effective than using replicas for read offloading.
- ✓
Use read replicas to offload reporting queries.
Why this is correct
Read replicas serve read-only traffic without impacting the primary.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates confuse materialized views (which still run on the primary) with read replicas (which offload the query execution entirely), leading them to choose A instead of D.
Detailed technical explanation
How to think about this question
Cloud SQL read replicas use PostgreSQL's streaming replication protocol (WAL-based) to maintain near-real-time consistency, typically with a lag of seconds. For reporting queries that can tolerate slight staleness, this is ideal. Under the hood, the replica applies WAL records asynchronously, so heavy reporting queries on the replica do not block the primary's commit operations. In a real-world scenario, a platform with 50:50 read/write ratio might see transactional latency drop by 60% after offloading reporting to replicas.
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 cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
What to study next
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FAQ
Questions learners often ask
What does this PCDE question test?
Design and implement database schemas — This question tests Design and implement database schemas — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use read replicas to offload reporting queries. — Option D is correct because read replicas in Cloud SQL for PostgreSQL allow you to offload read-only queries, such as complex reporting joins, from the primary instance. This separation reduces contention for CPU, memory, and I/O resources, preserving transactional performance. Read replicas are asynchronous and can handle heavy analytical workloads without impacting the primary's write path.
What should I do if I get this PCDE 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.
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Last reviewed: Jul 4, 2026
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