Question 1,505 of 1,663
DBS-C01 Workload-Specific Database Design Practice Question
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?
⚠ Common exam trap
Many exam-takers 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.
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
✓
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.
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 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.
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Last reviewed: Jun 24, 2026
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