DBS-C01 Management and Operations Practice Question
A company is using Amazon ElastiCache for Redis to cache database query results. They notice that the cache hit ratio is low and many requests are hitting the database. The 'Evictions' metric is high. What is the MOST likely cause?
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 cache node is too small for the workload.
The high 'Evictions' metric indicates that the cache node is constantly full, causing it to evict old data to make room for new data. This leads to a low cache hit ratio because frequently accessed items are evicted and must be fetched from the database. Option D correctly identifies that the cache node is too small for the workload. Option A is incorrect because insufficient replication factor would affect availability, not evictions. Option B is incorrect because encryption in transit does not impact cache capacity or evictions. Option C is incorrect because high network latency would affect request latency but not directly cause evictions.
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 replication factor is insufficient.
Why it's wrong here
Replication affects redundancy, not evictions.
- ✗
Encryption in transit is enabled.
Why it's wrong here
Encryption adds overhead but does not cause evictions.
- ✗
The application is experiencing high network latency.
Why it's wrong here
Network latency affects request time but not evictions.
- ✓
The cache node is too small for the workload.
Why this is correct
A small cache leads to frequent evictions, reducing the cache hit ratio.
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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 company is using Amazon ElastiCache for Redis to cache database query results. The application team reports that cache hit ratio has dropped significantly. What is the first step to investigate?
easy- A.Run the Redis INFO command to see memory usage
- B.Review the ElastiCache event logs for node failures
- ✓ C.Check the CacheHitRate and Evictions metrics in CloudWatch
- D.Check the Redis AOF persistence logs
Why C: When the cache hit ratio drops significantly, the first step is to investigate whether the cache is evicting keys due to memory pressure or if the working set no longer fits. CloudWatch metrics such as `CacheHitRate` and `Evictions` provide immediate visibility into these conditions without requiring direct Redis access. This aligns with the AWS Well-Architected Framework's principle of observability before making configuration changes.
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.