SAA-C03 Design High-Performing Architectures Practice Question
Exhibit
Current deployment summary: - 48 EC2 instances run a tightly coupled simulation engine. - Instances are spread across us-east-1a and us-east-1b. - Each worker exchanges small TCP messages every 5-10 ms with all other workers. - Measured east-west RTT: 4.9 ms average, 17.2 ms p95. - The application owner states that the workload can run in a single Availability Zone if that improves performance. - No external clients access the cluster directly.
Based on the exhibit, what change should the team make to achieve the lowest possible network latency for the distributed workload?
⚠ Common exam trap
Test-takers frequently assume multi-AZ is always better for high availability, but for latency-sensitive distributed workloads, a single-AZ cluster placement group is the correct choice to minimize inter-node latency, even though it sacrifices fault tolerance.
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
✓
Move the workload into a cluster placement group in one Availability Zone.
A cluster placement group provides the lowest possible network latency and highest throughput by placing all instances in a single Availability Zone with low-latency, non-blocking 10 Gbps or 25 Gbps network connectivity between them. This is ideal for tightly coupled, distributed workloads that require frequent inter-node communication, such as HPC or data analytics jobs.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Place the instances in a spread placement group across multiple Availability Zones.
Why it's wrong here
Spread placement groups are designed to reduce correlated failure risk, not to minimize latency between tightly coupled nodes. Spreading instances across Availability Zones also adds network distance and does not improve east-west communication. This would make the cluster more resilient in some cases, but it works against the stated performance goal.
When this WOULD be correct
A question asks for the highest availability and fault tolerance for a critical application that must survive an entire AZ failure, and latency is not the primary concern. Spread placement groups across AZs would be correct.
- ✓
Move the workload into a cluster placement group in one Availability Zone.
Why this is correct
Cluster placement groups place instances physically close together inside one Availability Zone, which is the best AWS option for workloads that need low-latency, high-bandwidth communication between many nodes. The exhibit explicitly says the workload can run in a single AZ if performance improves. That makes cluster placement groups the right fit.
- ✗
Add an Application Load Balancer in front of the workers to reduce inter-node latency.
Why it's wrong here
An Application Load Balancer helps distribute client traffic to application targets, but it does not reduce latency between worker nodes that are already talking to each other directly. It would introduce another hop for incoming traffic and does nothing to change physical placement of the instances.
When this WOULD be correct
This option would be correct in a question asking how to distribute incoming client requests across multiple EC2 instances in different Availability Zones for high availability and fault tolerance, while also providing health checks and SSL termination.
- ✗
Increase the EC2 instance size while keeping the current multi-AZ layout.
Why it's wrong here
Larger instances may improve CPU or memory headroom, but they do not solve the core issue shown in the exhibit: network latency between workers. The RTT problem is caused by placement and topology, not lack of compute capacity. Keeping the current AZ spread preserves the latency penalty.
When this WOULD be correct
This option would be correct in a scenario where the workload is compute-bound and requires more CPU or memory per instance, and the goal is to improve throughput or reduce processing time, not network latency.
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.
✓Move the workload into a cluster placement group in one Availability Zone.Correct answer▾
Why this is correct
Cluster placement groups place instances physically close together inside one Availability Zone, which is the best AWS option for workloads that need low-latency, high-bandwidth communication between many nodes. The exhibit explicitly says the workload can run in a single AZ if performance improves. That makes cluster placement groups the right fit.
✗Place the instances in a spread placement group across multiple Availability Zones.Wrong answer — click to see why▾
Why this is wrong here
Spread placement groups maximize availability and fault isolation by placing instances on distinct hardware across multiple AZs, which increases network latency due to physical separation. The goal is lowest possible latency, which requires a cluster placement group in a single AZ.
★ When this WOULD be the correct answer
A question asks for the highest availability and fault tolerance for a critical application that must survive an entire AZ failure, and latency is not the primary concern. Spread placement groups across AZs would be correct.
Why candidates choose this
Candidates may think that distributing instances across AZs always improves performance, confusing high availability with low latency, or they may overvalue fault tolerance when the question prioritizes latency.
✗Add an Application Load Balancer in front of the workers to reduce inter-node latency.Wrong answer — click to see why▾
Why this is wrong here
An Application Load Balancer distributes incoming traffic across targets, but it does not reduce inter-node latency between workers; in fact, it adds a hop and increases latency for node-to-node communication.
★ When this WOULD be the correct answer
This option would be correct in a question asking how to distribute incoming client requests across multiple EC2 instances in different Availability Zones for high availability and fault tolerance, while also providing health checks and SSL termination.
Why candidates choose this
Candidates may think that load balancers always improve performance, confusing load distribution for user-facing traffic with reducing latency for internal distributed workloads.
✗Increase the EC2 instance size while keeping the current multi-AZ layout.Wrong answer — click to see why▾
Why this is wrong here
Increasing EC2 instance size does not reduce network latency between instances; it improves compute capacity. The question specifically asks for lowest network latency, which requires physical proximity, not larger instances.
★ When this WOULD be the correct answer
This option would be correct in a scenario where the workload is compute-bound and requires more CPU or memory per instance, and the goal is to improve throughput or reduce processing time, not network latency.
Why candidates choose this
Candidates may assume larger instances have better network performance or that more resources inherently reduce latency, confusing compute capacity with network characteristics.
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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