This DBS-C01 practice question tests your understanding of workload-specific database design. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 company runs a customer-facing application on Amazon RDS for MySQL. The application experiences frequent read replicas lagging behind the primary due to long-running analytics queries. The analytics team runs complex SELECT queries that scan large tables. Which design change would minimize replica lag without affecting production writes?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "primary"
Why it matters: Asks for the main purpose or function, not a secondary benefit. Eliminate answers that describe side-effects or partial functions.
Clue: "minimum / minimize"
Why it matters: Asks for the least resource use — fewest addresses, smallest subnet, lowest overhead. Eliminate over-provisioned options even if they would technically work.
Use Amazon DynamoDB Accelerator (DAX) for caching.
Why wrong: DAX is for DynamoDB, not RDS.
Increase the instance size of the primary and all read replicas.
Why wrong: Increases cost and may not fully isolate analytics.
Enable Multi-AZ on the primary instance.
Why wrong: Multi-AZ provides failover, not read scaling.
Create a cross-Region read replica for analytics queries.
Offloads analytics to a separate replica, reducing lag.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Create a cross-Region read replica for analytics queries.
Creating a cross-Region read replica for analytics queries offloads the long-running SELECT statements to a separate read replica in a different AWS Region, isolating the analytics workload from the primary instance and its in-Region replicas. This prevents the analytics queries from competing for I/O and CPU resources on the primary or its local replicas, thereby minimizing replica lag without affecting production writes. Cross-Region replicas use asynchronous replication, so they can handle heavy read traffic without impacting the primary's write performance.
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.
Use Amazon DynamoDB Accelerator (DAX) for caching.
Why it's wrong here
DAX is for DynamoDB, not RDS.
Increase the instance size of the primary and all read replicas.
Why it's wrong here
Increases cost and may not fully isolate analytics.
Enable Multi-AZ on the primary instance.
Why it's wrong here
Multi-AZ provides failover, not read scaling.
Create a cross-Region read replica for analytics queries.
Why this is correct
Offloads analytics to a separate replica, reducing lag.
Clue confirmation
The clue words "primary", "minimum / minimize" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
The trap here is that candidates often assume increasing instance size (Option B) or enabling Multi-AZ (Option C) will solve replica lag, but they fail to recognize that the lag is caused by resource contention from analytics queries on the same replicas, not by insufficient hardware or lack of high availability.
Detailed technical explanation
Cross-Region read replicas in RDS for MySQL use MySQL's native asynchronous replication (binlog-based) across AWS Regions, which means the replica can lag due to network latency, but the analytics queries run on the replica do not affect the primary's write throughput. The key benefit is workload isolation: by directing complex SELECT queries to a dedicated replica in a different Region, you avoid contention for I/O and CPU on the primary and its in-Region replicas, which is the root cause of replica lag in this scenario. This design is particularly effective when analytics queries are long-running and scan large tables, as they would otherwise consume resources on the same replicas used for production read traffic.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
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
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
Workload-Specific Database Design — This question tests Workload-Specific Database Design — Read the scenario before looking for a memorised answer..
The correct answer is: Create a cross-Region read replica for analytics queries. — Creating a cross-Region read replica for analytics queries offloads the long-running SELECT statements to a separate read replica in a different AWS Region, isolating the analytics workload from the primary instance and its in-Region replicas. This prevents the analytics queries from competing for I/O and CPU resources on the primary or its local replicas, thereby minimizing replica lag without affecting production writes. Cross-Region replicas use asynchronous replication, so they can handle heavy read traffic without impacting the primary's write performance.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Yes — watch for: "primary", "minimum / minimize". Asks for the main purpose or function, not a secondary benefit. Eliminate answers that describe side-effects or partial functions.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
This DBS-C01 practice question is part of Courseiva's free Amazon Web Services 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 DBS-C01 exam.
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