PCD Practice Question: Designing highly scalable, available, and reliable cloud-native applications
This PCD practice question tests your understanding of designing highly scalable, available, and reliable cloud-native applications. 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.
A web application uses Cloud SQL for MySQL. The team expects a sudden spike in read-only traffic from a reporting tool. What should they use to offload read queries?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Read replicas
Read replicas in Cloud SQL for MySQL allow you to offload read traffic from the primary instance by creating one or more read-only copies. This is the correct approach for handling a sudden spike in read-only queries from a reporting tool, as it distributes the load without affecting write performance or requiring application changes beyond updating the connection string.
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.
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Automatic storage increase
Why it's wrong here
Automatic storage increase addresses capacity, not read performance.
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Cross-region replication
Why it's wrong here
Cross-region replication is primarily for disaster recovery, not for offloading read queries.
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Read replicas
Why this is correct
Read replicas allow you to offload read queries from the primary instance, improving performance.
Related concept
Read the scenario before looking for a memorised answer.
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Failover replica
Why it's wrong here
Failover replicas are for high availability, not for distributing read traffic.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Cisco often tests the distinction between read replicas (for scaling reads) and failover replicas (for high availability), tempting candidates to choose failover replica because it sounds like it can handle traffic, but it cannot serve reads independently in Cloud SQL for MySQL.
Detailed technical explanation
How to think about this question
Cloud SQL read replicas use asynchronous replication based on MySQL's native binlog replication, meaning they may lag slightly behind the primary (typically milliseconds to seconds). For reporting tools that can tolerate eventual consistency, this is ideal; however, if the application requires strongly consistent reads, the read replica should be avoided or the application must verify replication lag. In a real-world scenario, you can create multiple read replicas in the same region and use a connection pooler or proxy to distribute queries, scaling horizontally to handle massive read spikes.
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.
Designing highly scalable, available, and reliable cloud-native applications — This question tests Designing highly scalable, available, and reliable cloud-native applications — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Read replicas — Read replicas in Cloud SQL for MySQL allow you to offload read traffic from the primary instance by creating one or more read-only copies. This is the correct approach for handling a sudden spike in read-only queries from a reporting tool, as it distributes the load without affecting write performance or requiring application changes beyond updating the connection string.
What should I do if I get this PCD 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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Question Discussion
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