SAA-C03 Design High-Performing Architectures Practice Question
Your company needs a high-throughput, low-latency TCP service using a custom binary protocol. Requirements: preserve the original client source IP for rate limiting, keep latency minimal, and use TCP health checks. The current setup uses an Application Load Balancer and performance is inconsistent. Which load balancer choice best meets these requirements?
⚠ Common exam trap
Candidates often assume Application Load Balancers preserve client source IP for all protocols, but they only do so for HTTP/HTTPS traffic via the X-Forwarded-For header, not for raw TCP traffic, and they introduce higher latency due to Layer 7 processing.
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 Network Load Balancer (NLB) with TCP listeners so traffic stays at Layer 4 and the original source IP is preserved.
A Network Load Balancer (NLB) operates at Layer 4 and preserves the original client source IP by default, which is essential for accurate rate limiting. Its TCP listeners provide low-latency, high-throughput handling of custom binary protocols, and it supports TCP health checks natively. This directly addresses the performance inconsistency seen with the Application Load Balancer, which operates at Layer 7 and introduces additional processing overhead.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Keep the Application Load Balancer (ALB), because ALBs also preserve client source IP for TCP protocols.
Why it's wrong here
ALBs are optimized for Layer 7 (HTTP/HTTPS) routing semantics. For a custom binary TCP protocol, ALB behavior and feature set do not align as well with pure Layer 4 TCP health checking and consistently low-latency forwarding. Using ALB for generic TCP services is commonly a poor fit compared to an NLB.
- ✓
Use a Network Load Balancer (NLB) with TCP listeners so traffic stays at Layer 4 and the original source IP is preserved.
Why this is correct
NLB is designed for Layer 4 TCP/UDP traffic with very low latency and high throughput. It supports TCP health checks and preserves the original client source IP by default, which enables accurate client-IP-based rate limiting for a custom TCP protocol.
- ✗
Use Amazon API Gateway because it preserves client source IP and provides TCP health checks for all protocols.
Why it's wrong here
API Gateway is intended for HTTP APIs, REST APIs, and WebSockets. It is not designed to proxy arbitrary custom TCP binary protocols with Layer 4 TCP health checks, so it does not satisfy the core protocol/health-check and latency requirements.
- ✗
Use Amazon CloudFront with an S3 origin, because CloudFront reduces latency for TCP-based protocols.
Why it's wrong here
CloudFront is primarily an HTTP(S) distribution service and does not function as a Layer 4 TCP load balancer for a custom TCP binary protocol with TCP health checks. S3 origins are also not an appropriate backend for a live TCP service response path.
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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.