DBS-C01 Monitoring and Troubleshooting Practice Question
A startup is using Amazon ElastiCache for Redis to cache session data. They deployed a single Redis node (cache.t3.micro) in us-west-2. The application reports high latency when reading session data. CloudWatch metrics show CPUUtilization at 90% and Evictions at 100 per minute. The cache hit ratio is 80%. The database specialist suspects the node is overloaded. What should the specialist do to improve performance?
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
✓
Scale up to a larger node type, such as cache.m5.large.
Scale up to a larger node type, such as cache.m5.large. The current node (cache.t3.micro) is overloaded, as indicated by high CPU utilization (90%) and frequent evictions (100/min). Scaling up provides more CPU and memory resources, reducing evictions and lowering latency. Option B (add a read replica) does not help because the issue is on the primary node; read replicas are for scaling read-heavy workloads on a primary, but here the primary is overloaded. Option C (enable cluster mode) is not suitable for a single-node setup and adds complexity; it is intended for partitioning data across multiple shards. Option D (decrease TTL) would reduce memory usage but may increase cache misses and does not address the CPU bottleneck; it could actually worsen performance by requiring more database reads.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Scale up to a larger node type, such as cache.m5.large.
Why this is correct
More resources reduce CPU and evictions.
- ✗
Add a read replica to offload read traffic.
Why it's wrong here
Read replicas are for read-heavy workloads; the issue is overall load.
- ✗
Enable cluster mode and add more shards.
Why it's wrong here
Cluster mode adds sharding overhead; not suitable for session data on a small node.
- ✗
Decrease the TTL for session keys to reduce memory usage.
Why it's wrong here
Reducing TTL increases cache misses, worsening performance.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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