SAA-C03 Design High-Performing Architectures Practice Question
Exhibit
Amazon CloudWatch metrics for the instance volume: - VolumeType: gp2 - VolumeSize: 1 TiB - ReadOps: 9,000-11,000 sustained - WriteOps: 8,000-10,000 sustained - BurstBalance: 0% for long periods - VolumeQueueLength: elevated during peak use - VolumeReadLatency p95: 23 ms - VolumeWriteLatency p95: 19 ms Application note: - The working set is random and latency-sensitive - The storage requirement is persistent block storage attached to one instance
Based on the exhibit, a single EC2 instance hosts a latency-sensitive cache that performs sustained random reads and writes to persistent block storage. The current EBS volume is a general-purpose SSD, but BurstBalance is repeatedly depleted and p95 I/O latency has risen above 20 ms. The workload needs more than 16,000 sustained IOPS. Which change is the best fix?
⚠ Common exam trap
Many candidates assume increasing instance size (Option C) will improve EBS performance, but EBS IOPS and throughput are tied to the volume type and size, not the instance type (except for EBS-optimized bandwidth), so the gp2 burst credit exhaustion remains the root 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
✓
Replace the volume with an io2 EBS volume and provision the required IOPS.
The workload requires more than 16,000 sustained IOPS with low latency, and the gp2 volume's burst credits are exhausted, causing high latency. An io2 Block Express or io2 volume can be provisioned with the exact IOPS needed (up to 256,000 IOPS) and provides consistent single-digit millisecond latency, making it the best fix for this latency-sensitive, sustained I/O workload.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Move the data to Amazon S3 so the instance can read and write objects directly.
Why it's wrong here
Amazon S3 is object storage and does not provide a directly attached block device interface. It is not an appropriate replacement for a latency-sensitive cache that requires persistent block storage semantics and low-latency random I/O.
- ✓
Replace the volume with an io2 EBS volume and provision the required IOPS.
Why this is correct
io2 is designed for mission-critical workloads that need sustained, predictable, low-latency random I/O. Unlike gp2, it does not depend on burst credits for performance. Provisioning the required IOPS directly addresses the exhausted BurstBalance and the sustained throughput requirement above 16,000 IOPS.
- ✗
Keep gp2 and increase the instance size to a compute-optimized family.
Why it's wrong here
The metrics point to a storage bottleneck, not a CPU bottleneck. A larger instance may increase compute capacity, but it does not remove the gp2 burst-credit limitation or guarantee the sustained IOPS level and latency profile that the workload requires.
- ✗
Enable Amazon EFS with bursting throughput mode for the cache data.
Why it's wrong here
Amazon EFS is a shared file system, not a direct attached block volume. Bursting throughput mode also does not provide the same low-latency, high-IOPS characteristics needed for a single-instance cache with sustained random block reads and writes.
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