SAA-C03 Design Secure Architectures Practice Question
A team runs a CPU-intensive image processing service on Amazon EC2. The service spends most of its time resizing and compressing images, and the team wants the best price-performance starting point for compute-heavy work. Which EC2 instance family should they choose?
⚠ Common exam trap
A common mix-up: candidates confuse 'CPU-intensive' with 'memory-intensive' or 'storage-intensive' and choose a general purpose instance (D) thinking it is a safe default, but the question specifically asks for the best price-performance starting point for compute-heavy work, which is the compute optimized family.
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
✓
Compute optimized instances
Compute optimized instances (C family) are designed for workloads that benefit from high-performance processors, such as batch processing, media transcoding, and image processing. Since the team's service is CPU-intensive (resizing and compressing images), the C family provides the best price-performance starting point for compute-heavy work.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Memory optimized instances
Why it's wrong here
Memory optimized instances, such as R5 or X2g, are engineered for workloads that require large amounts of RAM, like in-memory databases, real-time analytics, or large caches. An image processing service is not typically memory-bound; its performance depends on the ability to execute CPU instructions quickly, so selecting these instances would leave the CPU bottleneck unresolved while paying a premium for unused memory capacity.
When this WOULD be correct
A question describing a service that processes large in-memory databases or real-time big data analytics, where the primary bottleneck is memory capacity and throughput, would make memory optimized instances the correct choice.
- ✓
Compute optimized instances
Why this is correct
Compute optimized instances, such as the C5 or C6g families, provide the highest vCPU-to-memory ratio and are purpose-built for CPU-intensive workloads like image processing, scientific modeling, and video encoding. Their enhanced clock speeds and sustained compute performance directly target the processing bottleneck, making them the most efficient and cost-effective choice for this workload.
- ✗
Storage optimized instances
Why it's wrong here
Storage optimized instances, such as I3 or D2, are designed for very high sequential or random I/O to local block storage, commonly used in data warehousing and distributed file systems. While reading and writing image files does involve storage I/O, the primary constraint of a CPU-intensive image processing service is the compute capacity, not disk throughput, so these instances would not meaningfully improve processing speed and are not the recommended family.
When this WOULD be correct
A question asking for an EC2 instance family optimized for workloads that require high, sequential read/write access to very large datasets stored locally on the instance, such as distributed file systems, data warehousing, or log processing.
- ✗
General purpose instances
Why it's wrong here
General purpose instances, such as M5 or M6g, offer a balanced mix of compute, memory, and networking, making them ideal for web servers, small databases, and development environments. For a CPU-intensive image processing service, the memory capacity is often underutilized while the CPU is saturated, so these instances would require more vCPUs or larger sizes to match the throughput of a compute-optimized instance, increasing complexity and cost.
When this WOULD be correct
A question asks for a balanced instance family for a web application with moderate CPU and memory usage, where cost and flexibility are priorities, and no specific resource is a bottleneck.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The SAA-C03 exam frequently reuses these exact scenarios with slightly different constraints.
✓Compute optimized instancesCorrect answer▾
Why this is correct
Compute optimized instances, such as the C5 or C6g families, provide the highest vCPU-to-memory ratio and are purpose-built for CPU-intensive workloads like image processing, scientific modeling, and video encoding. Their enhanced clock speeds and sustained compute performance directly target the processing bottleneck, making them the most efficient and cost-effective choice for this workload.
✗Memory optimized instancesWrong answer — click to see why▾
Why this is wrong here
Memory optimized instances are designed for workloads that process large datasets in memory, not for CPU-intensive tasks like image resizing and compression, which primarily require high compute power.
★ When this WOULD be the correct answer
A question describing a service that processes large in-memory databases or real-time big data analytics, where the primary bottleneck is memory capacity and throughput, would make memory optimized instances the correct choice.
Why candidates choose this
Candidates may mistakenly think that image processing requires large amounts of memory, or they may confuse memory-intensive workloads with compute-intensive ones.
✗Storage optimized instancesWrong answer — click to see why▾
Why this is wrong here
Storage optimized instances are designed for workloads with high sequential I/O access to large datasets on local storage, not for CPU-intensive image processing tasks like resizing and compressing images.
★ When this WOULD be the correct answer
A question asking for an EC2 instance family optimized for workloads that require high, sequential read/write access to very large datasets stored locally on the instance, such as distributed file systems, data warehousing, or log processing.
Why candidates choose this
Candidates may mistakenly think image processing involves heavy disk I/O due to reading/writing many image files, leading them to choose storage optimized instances instead of focusing on the CPU-bound nature of the task.
✗General purpose instancesWrong answer — click to see why▾
Why this is wrong here
General purpose instances balance compute, memory, and networking, but for CPU-intensive image processing, compute optimized instances offer better price-performance due to higher vCPU count and faster clock speeds.
★ When this WOULD be the correct answer
A question asks for a balanced instance family for a web application with moderate CPU and memory usage, where cost and flexibility are priorities, and no specific resource is a bottleneck.
Why candidates choose this
Candidates may assume 'general purpose' is always a safe starting point, overlooking that CPU-intensive workloads benefit from specialized compute optimized instances for better performance per cost.
Analysis generated from the official SAA-C03blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
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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.