DEA-C01 Data Store Management Practice Question
A company runs a critical application on Amazon RDS for MySQL. To ensure high availability and automatic failover, the database is deployed as a Multi-AZ DB instance. The application uses read-heavy workloads. Which additional configuration should be used to offload read traffic without impacting write performance?
⚠ Common exam trap
Watch out — candidates often assume the Multi-AZ standby instance can be used for read queries, but AWS explicitly prevents this to ensure failover consistency, making Read Replicas the correct choice for offloading reads.
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 one or more Read Replicas in different AZs.
Amazon RDS Read Replicas are designed to offload read traffic from the primary DB instance without affecting write performance. Unlike the Multi-AZ standby instance, which is not accessible for reads, Read Replicas can be placed in different Availability Zones and serve read queries independently, improving read scalability while the primary handles writes.
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 the Multi-AZ standby instance for read queries.
Why it's wrong here
A Multi-AZ standby is a passive synchronous replica that accepts no reads; directing queries there is unsupported. Read replicas serve read traffic on separate instances. The standby exists solely for automatic failover, so it would be correct only as the failover target, not a read endpoint.
- ✓
Create one or more Read Replicas in different AZs.
Why this is correct
Read Replicas asynchronously replicate from the primary and serve read-only traffic, offloading SELECT queries while writes continue unaffected on the Multi-AZ primary. Placing them in different AZs also improves resilience, complementing the existing automatic failover configuration.
- ✗
Use Amazon ElastiCache to cache read queries.
Why it's wrong here
Caching read queries in ElastiCache reduces database load but does not offload read traffic to a separate database endpoint; it introduces cache-invalidation complexity and still leaves reads hitting MySQL on cache misses. It is tempting because ElastiCache genuinely accelerates repeated identical queries, and would be correct if the workload were dominated by hot, cacheable key-value lookups rather than needing a read replica.
- ✗
Change to a Single-AZ deployment with a larger instance size.
Why it's wrong here
Collapsing Multi-AZ to Single-AZ removes the standby and automatic failover, directly violating the high-availability requirement, while a larger instance scales writes and reads on one node rather than offloading reads elsewhere. It is tempting because vertical scaling does raise read throughput, and would be correct for a non-critical workload that tolerates downtime and needs raw capacity.
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