DBS-C01 Workload-Specific Database Design Practice Question
A company recently migrated their PostgreSQL database to Amazon Aurora PostgreSQL. They notice that the average query latency has increased, especially for complex read queries. The DB instance size is adequate and CPU utilization is below 50%. What is the MOST likely cause of the increased latency?
⚠ Common exam trap
It's easy for candidates to assume low CPU utilization means the instance is not overloaded, but they overlook that query latency can increase due to lock contention, connection pooling limits, or misrouted traffic rather than CPU saturation.
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
✓
The application is sending all read queries to the primary instance instead of offloading them to Aurora Replicas.
If all read queries are sent to the primary (writer) instance, it must handle both writes and reads, leading to contention and increased latency. Aurora Replicas are designed to offload read traffic, and by not using them, the primary instance becomes a bottleneck even if CPU utilization is low. This is a common misconfiguration after migration, as applications often retain the original connection string pointing to the primary endpoint.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The Auto Scaling policy for the Aurora cluster is set to scale down too aggressively.
Why it's wrong here
Auto Scaling does not directly cause increased latency; it may cause minor disruption during scaling.
- ✗
The Aurora cluster volume uses a smaller buffer cache than the original RDS instance.
Why it's wrong here
Aurora uses a shared storage volume; the buffer cache is on the instance, and if the instance class is the same, cache size is similar.
- ✗
The Aurora cluster is using the parallel query feature which adds overhead for complex queries.
Why it's wrong here
Parallel query is designed to improve performance for analytical queries, not degrade it.
- ✓
The application is sending all read queries to the primary instance instead of offloading them to Aurora Replicas.
Why this is correct
Without using Aurora Replicas, the primary handles all read traffic, leading to contention and higher latency.
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Same concept, more angles
1 more way this is tested on DBS-C01
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A financial services company runs an Amazon Aurora MySQL database. The application performs complex joins and aggregations on large tables, causing high CPU utilization on the writer instance. The team wants to reduce load without changing the application code. Which solution would best address this issue?
hard- ✓ A.Create one or more Aurora Replicas and route read traffic to them.
- B.Switch to asynchronous replication to reduce load on the primary.
- C.Enable Aurora Auto Scaling to increase storage capacity.
- D.Migrate to Aurora Serverless v2 for automatic scaling.
Why A: Creating one or more Aurora Replicas and routing read traffic to them offloads the complex joins and aggregations from the writer instance, reducing CPU utilization without requiring application code changes. Aurora Replicas share the same underlying storage volume as the writer, so they serve read queries with minimal replication lag while the writer focuses on write operations.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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.