How to Migrate a Custom TCP Protocol Application to AWS with Low Latency
A company is migrating a legacy on-premises application that uses a custom TCP protocol. The application needs to be accessible from the internet while maintaining security. Which AWS service should they use to expose the application without modifying the code?
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
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Network Load Balancer (NLB)
Network Load Balancer (NLB) because it operates at Layer 4 (TCP) and can handle custom TCP protocols without requiring application modifications. Option A (CloudFront) is a content delivery network that only supports HTTP/HTTPS. Option C (API Gateway) is designed for HTTP/HTTPS APIs and does not handle raw TCP traffic. Option D (Application Load Balancer, ALB) operates at Layer 7 (HTTP/HTTPS) and cannot process custom TCP protocols.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
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Amazon CloudFront
Why it's wrong here
Amazon CloudFront terminates HTTP/HTTPS at edge locations, so it cannot proxy a custom TCP protocol without code changes. It is tempting because CloudFront accelerates and secures web workloads, and would be the right choice for exposing an HTTP or HTTPS application globally with caching and TLS termination.
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Network Load Balancer (NLB)
Why this is correct
Network Load Balancer operates at layer 4, forwarding arbitrary TCP traffic to targets while preserving source IP, so the custom protocol works unmodified. It satisfies the no-code-change constraint and supports internet-facing exposure with TLS termination.
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Amazon API Gateway
Why it's wrong here
API Gateway exposes REST, HTTP and WebSocket APIs, terminating those protocols rather than forwarding raw custom TCP. It is correct for building managed APIs over HTTP backends, but here the custom TCP protocol must pass through unmodified.
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Application Load Balancer (ALB)
Why it's wrong here
ALB terminates HTTP/HTTPS and routes on layer 7 attributes; it cannot forward arbitrary custom TCP protocols. It is tempting because ALB provides internet-facing load balancing with TLS and health checks, and would be right for HTTP or gRPC workloads. Here the custom TCP protocol requires a Network Load Balancer, which handles TCP at layer 4.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This SAP-C02 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 SAP-C02 exam.