ANS-C01 Network Design Practice Question
A company is designing a network for a real-time trading application that requires extremely low latency (sub-millisecond) between two EC2 instances located in the same AWS region. The instances are in different Availability Zones. The trading application uses a proprietary protocol over TCP. The company wants to minimize latency as much as possible. They are considering using a placement group. Which type of placement group should they use, and what network optimization should they apply?
⚠ Common exam trap
AWS often tests the misconception that a cluster placement group can span multiple Availability Zones, but in reality, it is confined to a single AZ to guarantee low-latency physical proximity.
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
✓
Use a cluster placement group for both instances and enable enhanced networking (SR-IOV)
A cluster placement group is the only placement group type that provides low-latency, high-bandwidth network performance by placing instances in a single Availability Zone within the same rack. Enhanced networking using SR-IOV (Single Root I/O Virtualization) bypasses the hypervisor's network stack, reducing per-packet processing latency and jitter, which is critical for sub-millisecond trading traffic over TCP.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Use a spread placement group and enable dedicated tenancy
Why it's wrong here
Spread placement group does not optimize latency; dedicated tenancy adds overhead.
- ✗
Use a partition placement group and enable EBS-optimized instances
Why it's wrong here
Partition placement group is for fault tolerance, not latency.
- ✓
Use a cluster placement group for both instances and enable enhanced networking (SR-IOV)
Why this is correct
Cluster placement group provides low latency; enhanced networking reduces overhead.
- ✗
Use a cluster placement group but launch instances in different Availability Zones
Why it's wrong here
Cluster placement group cannot span AZs.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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