Low Latency EC2 with Cluster Placement Groups
A company is designing a network for a critical application that requires low latency and high throughput between EC2 instances in the same AWS Region. Which network design should the company use?
Quick Answer
The answer is to launch the instances in a Cluster Placement Group. This is the correct choice because a cluster placement group provides the lowest possible latency and highest throughput between EC2 instances by placing them in a single Availability Zone with non-blocking, high-bandwidth networking, which is essential for tightly coupled, latency-sensitive applications. On the AWS Certified Advanced Networking Specialty ANS-C01 exam, this concept tests your understanding of placement group types and their network performance characteristics; a common trap is confusing a spread or partition placement group, which prioritize fault tolerance over low latency. For low latency EC2 instances in a cluster placement group, remember that all instances must be in the same AZ and launched into the group at the same time to benefit from the dedicated 10 Gbps or 100 Gbps per-flow bandwidth. Memory tip: think “Cluster = Clustered in one AZ for low latency, like a tightly packed cluster of servers.”
⚠ Common exam trap
A common mix-up: candidates confuse 'enhanced networking' (Option C) as a standalone solution for low latency, overlooking that placement group optimization is required to achieve the lowest possible latency and highest throughput, even with enhanced networking enabled.
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
✓
Launch the instances in a Cluster Placement Group.
A Cluster Placement Group is the correct choice because it provides the lowest possible latency and highest throughput between EC2 instances by placing them in a single Availability Zone with non-blocking, high-bandwidth networking. This design is ideal for tightly coupled, high-performance computing (HPC) or latency-sensitive applications that require consistent, low-latency communication within the same AWS Region.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Launch the instances in a Cluster Placement Group.
Why this is correct
Cluster Placement Groups provide low-latency, high-throughput networking.
- ✗
Launch the instances in a Spread Placement Group.
Why it's wrong here
Spread Placement Groups are for fault isolation, not performance.
- ✗
Launch the instances as larger instance types with enhanced networking.
Why it's wrong here
While enhanced networking helps, placement is key for low latency.
- ✗
Launch the instances in different Availability Zones.
Why it's wrong here
Cross-AZ traffic introduces higher latency.
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Same concept, more angles
2 more ways this is tested on ANS-C01
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company is designing a network for a critical application that requires low-latency communication between EC2 instances in the same AWS Region. They want to maximize network throughput and minimize latency. Which TWO design choices should they make? (Choose two.)
medium- A.Attach an internet gateway to the VPC and route traffic through it.
- ✓ B.Enable enhanced networking (ENA) on the EC2 instances.
- C.Use a VPN connection to route traffic between instances.
- D.Use a spread placement group for the EC2 instances.
- ✓ E.Place the EC2 instances in a cluster placement group.
Why B: Enabling Enhanced Networking (ENA) on EC2 instances provides higher bandwidth, higher packet-per-second (PPS) performance, and consistently lower inter-instance latencies by using a modern network interface driver that offloads network processing to dedicated hardware. This is essential for critical applications requiring maximum throughput and minimal latency within the same AWS Region.
Variation 2. A company is designing a network for a critical application that requires low latency between EC2 instances. The instances are in the same AWS Region but different Availability Zones. Which configuration will provide the lowest latency?
hard- A.Use an Application Load Balancer to distribute traffic
- ✓ B.Launch instances in the same placement group within a single Availability Zone
- C.Use Direct Connect to connect the VPCs
- D.Use VPC peering to connect the VPCs
Why B: Placing EC2 instances within the same placement group in a single Availability Zone ensures they are in close physical proximity, often on the same rack or within the same cluster, which minimizes network hops and achieves the lowest possible latency (typically under 1 ms). This configuration is specifically designed for low-latency, high-throughput workloads like HPC or real-time data processing.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This ANS-C01 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 ANS-C01 exam.