Quick Answer
The answer is to add read replicas. This is the correct choice because read replicas in Cloud SQL for MySQL provide horizontal read scalability by offloading product catalog queries from the primary instance, using MySQL’s native asynchronous binary log replication to keep replicas current while the primary focuses on write operations. On the Google Professional Cloud Database Engineer exam, this scenario tests your understanding of Cloud SQL’s read scaling patterns versus alternatives like connection pooling or caching; a common trap is confusing read replicas with failover replicas or assuming synchronous replication is used for read scaling. Remember that read replicas are for read-heavy workloads only—they do not improve write performance. A useful memory tip: think “read replicas for reads, primary for writes,” and note that replicas can be promoted but are not designed for high-availability failover in MySQL unless configured as a regional replica.
This PCDE practice question tests your understanding of plan and manage database infrastructure. 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 site uses Cloud SQL for MySQL. They need read scalability for product catalog queries. What should they do?
Add read replicas
Read replicas serve read queries, reducing load on the primary.
Partition tables
Why wrong: Partitioning helps manage large tables but does not provide additional read capacity.
Use Cloud Spanner
Why wrong: Cloud Spanner is a different database requiring application changes.
Enable automatic storage increase
Why wrong: Automatic storage increase only adds disk space, not read capacity.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Add read replicas
Adding read replicas in Cloud SQL for MySQL offloads read traffic from the primary instance, providing horizontal read scalability for product catalog queries. Replicas asynchronously replicate data using MySQL's native binary log replication, allowing the primary to focus on writes while replicas handle read-heavy workloads.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Add read replicas
Why this is correct
Read replicas serve read queries, reducing load on the primary.
Related concept
Read the scenario before looking for a memorised answer.
Partition tables
Why it's wrong here
Partitioning helps manage large tables but does not provide additional read capacity.
Use Cloud Spanner
Why it's wrong here
Cloud Spanner is a different database requiring application changes.
Enable automatic storage increase
Why it's wrong here
Automatic storage increase only adds disk space, not read capacity.
Common exam traps
The trap here is that candidates confuse vertical scaling (storage increase) or schema-level optimizations (partitioning) with horizontal read scaling, or incorrectly assume a fully distributed database like Spanner is required for simple read offloading.
Detailed technical explanation
Cloud SQL read replicas use MySQL's asynchronous replication (based on binary log position or GTID) to maintain consistency, with a typical replication lag of seconds under normal load. In a real-world scenario, if the catalog is updated frequently (e.g., price changes), stale reads from replicas can occur; using 'read-only' transactions and monitoring lag via the 'Seconds_Behind_Master' metric is critical for application correctness.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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
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FAQ
Plan and manage database infrastructure — This question tests Plan and manage database infrastructure — Read the scenario before looking for a memorised answer..
The correct answer is: Add read replicas — Adding read replicas in Cloud SQL for MySQL offloads read traffic from the primary instance, providing horizontal read scalability for product catalog queries. Replicas asynchronously replicate data using MySQL's native binary log replication, allowing the primary to focus on writes while replicas handle read-heavy workloads.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 25, 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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