SAA-C03 Design High-Performing Architectures Practice Question
A data processing application runs on a single EC2 instance and needs persistent block storage with sustained low-latency random read/write performance (high IOPS). Which storage choice is most appropriate?
⚠ Common exam trap
Candidates often confuse throughput-optimized HDD (st1) with IOPS-optimized SSD (io2) because both are EBS volume types, but st1 is designed for sequential, not random, I/O workloads.
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
✓
EBS io2 provisioned IOPS SSD
Amazon EBS io2 Provisioned IOPS SSD volumes are designed for I/O-intensive workloads that require sustained, low-latency random read/write performance with high IOPS. They provide consistent performance by allowing you to provision a specific IOPS level (up to 256,000 IOPS per volume) and offer a 99.999% durability guarantee, making them ideal for a single EC2 instance needing persistent block storage.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
EBS io2 provisioned IOPS SSD
Why this is correct
Amazon EBS io2 is a block-level storage volume designed for low-latency, high-IOPS workloads. It provides provisioned IOPS with consistent performance, making it ideal for a single EC2 instance running data-processing applications that require high random I/O and low latency. Unlike other options, io2 volumes deliver 99.999% durability and are directly attached to the instance, ensuring minimal network overhead.
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Amazon S3 Standard
Why it's wrong here
Amazon S3 Standard is object storage, not block storage, meaning data is accessed via HTTP/S APIs rather than as a mounted file system. It has significantly higher latency (tens to hundreds of milliseconds) compared to EBS, and it cannot support random read/write operations at the block level. Therefore, it is unsuitable for a single EC2 instance requiring direct, low-latency storage for high-IOPS processing.
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Amazon EFS for POSIX file sharing between multiple instances
Why it's wrong here
Amazon EFS is a fully managed network file system that provides POSIX-compliant access, but it is designed for shared file access across multiple EC2 instances. Because it is accessed over the network, it introduces additional latency compared to instance-attached EBS volumes. For a single instance needing high, consistent IOPS, EFS's performance is limited by network throughput and file-system overhead, making it a poor choice for low-latency, high-IOPS block-level workloads.
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EBS Throughput Optimized HDD (st1) storage
Why it's wrong here
EBS Throughput Optimized HDD (st1) is a rotating hard-disk drive type optimized for large, sequential data transfers rather than random I/O. It offers low cost per gigabyte and high throughput, but its IOPS performance is limited, and it cannot provide provisioned IOPS or the low latency required for random-access data processing. The hdd-based design makes it fundamentally unsuitable for low-latency, high-IOPS applications, which are better served by SSD-backed volumes like io2.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This SAA-C03 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 SAA-C03 exam.