SAP-C02 Continuous Improvement for Existing Solutions Practice Question

A company uses Amazon RDS for MySQL with Multi-AZ deployment. The database experiences occasional read replica lag of up to 5 seconds. The application requires read-after-write consistency. Which action should the company take to improve the solution?

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

✓

Modify the application to always read from the primary instance.

Reading from the primary instance ensures read-after-write consistency. Since the application requires strong consistency, all reads must be directed to the primary, as read replicas may have lag. Option B is incorrect because increasing the number of read replicas does not reduce replication lag. Option C is incorrect because Amazon ElastiCache is a caching layer, not a solution for consistency. Option D is incorrect because Amazon RDS Proxy helps manage connections but does not eliminate read replica lag.

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

✓
Modify the application to always read from the primary instance.
Why this is correct
Read replicas are asynchronously updated, so lag of up to 5 seconds can return stale data. Directing all reads to the primary instance guarantees read-after-write consistency, because the primary always reflects the committed write, eliminating replica lag exposure.
✗
Increase the number of read replicas to distribute the load.
Why it's wrong here
Adding read replicas spreads query load but each replica still applies changes asynchronously, so lag persists. It is tempting because it scales read throughput, and would be correct when read capacity, not consistency, is the bottleneck.
✗
Implement Amazon ElastiCache to cache read results.
Why it's wrong here
ElastiCache serves cached copies that can be stale after a write, so read-after-write consistency is not guaranteed. It is tempting because it offloads repeated reads, and would be correct for read-heavy workloads tolerant of eventual consistency.
✗
Use Amazon RDS Proxy to route read queries to the read replica.
Why it's wrong here
RDS Proxy pools and shares database connections; it does not eliminate replica lag, so reads still return stale data. It is tempting because it improves scalability and failover, and would be correct for connection exhaustion or faster failover scenarios.

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SAP-C02 Continuous Improvement for Existing Solutions Practice Question

Why each option matters

Option-by-option breakdown

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