SAP-C02 Design for New Solutions Practice Question
A company is migrating a legacy monolithic application to AWS. The application uses a proprietary binary protocol over TCP. The company wants to modernize the architecture using microservices while minimizing changes to the client. Which approach should the company use?
⚠ Common exam trap
Candidates often assume an Application Load Balancer or API Gateway can handle any protocol because of their advanced routing features, but they forget that ALB and API Gateway are strictly Layer 7 (HTTP/HTTPS) and cannot process raw TCP or proprietary binary protocols.
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 with TCP listener and route traffic based on destination port to different target groups.
A Network Load Balancer (NLB) with a TCP listener can forward traffic based on destination port to different target groups, allowing the legacy client using a proprietary binary protocol over TCP to reach distinct microservices without any client-side changes. This preserves the existing TCP connection semantics and binary protocol, which an Application Load Balancer (HTTP/HTTPS only) or API Gateway (HTTP/REST) cannot handle.
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 Network Load Balancer with TCP listener and route traffic based on destination port to different target groups.
Why this is correct
A Network Load Balancer preserves the proprietary binary TCP protocol end to end, since it operates at layer 4 without parsing payloads. Port-based listener rules let a single NLB endpoint fan traffic out to separate microservice target groups, so existing clients keep their connection details unchanged.
- ✗
Use AWS Global Accelerator with a TCP listener and endpoint groups for microservices.
Why it's wrong here
Global Accelerator proxies TCP flows to endpoint groups but performs no protocol translation, so the proprietary binary protocol still reaches each microservice unchanged; clients cannot be decoupled. It is tempting for latency-based global TCP routing, which suits multi-Region acceleration rather than modernising a legacy protocol.
- ✗
Use an Application Load Balancer with path-based routing to direct traffic to separate microservices.
Why it's wrong here
An ALB inspects HTTP/HTTPS and routes on paths or headers, so it cannot parse the proprietary binary TCP protocol to select microservices. It is tempting because path-based routing is the standard microservice pattern, but that applies only when clients already speak HTTP.
- ✗
Use Amazon API Gateway with a custom authorizer to route requests to AWS Lambda functions.
Why it's wrong here
API Gateway exposes REST/HTTP endpoints and Lambda expects JSON or HTTP events, so the proprietary binary TCP protocol cannot traverse it without client changes. It is tempting because API Gateway plus Lambda is the canonical serverless microservice pattern, but only for HTTP-based clients.
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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.