The correct answer is to use a Network Load Balancer with a TCP listener and route traffic based on destination port to different target groups. This approach works because the NLB operates at Layer 4, preserving the proprietary binary protocol over TCP without requiring any changes to the client application, while the port-based routing allows you to direct traffic to distinct microservice target groups. On the AWS Certified Solutions Architect Professional SAP-C02 exam, this scenario tests your understanding of when to choose a Layer 4 load balancer over Layer 7 alternatives—a common trap is selecting an Application Load Balancer or API Gateway, which would force HTTP or REST onto a legacy TCP protocol, breaking client compatibility. Remember, when migrating legacy TCP protocols to microservices, keep it simple: NLB for TCP, ALB for HTTP. Memory tip: “TCP stays at Layer 4, so NLB is the door.”
SAP-C02 Design for New Solutions Practice Question
This SAP-C02 practice question tests your understanding of design for new solutions. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
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?
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.
Networking Load Balancer with TCP listener and target groups allows routing based on protocol without modifying clients. Option A (ALB) requires HTTP. Option C (API Gateway) requires REST. Option D (AWS Global Accelerator) uses anycast IP but still needs TCP routing.
Key principle: NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
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
NLB can handle TCP traffic and route based on port to different services.
Related concept
Static NAT maps one inside address to one outside address.
✗
Use AWS Global Accelerator with a TCP listener and endpoint groups for microservices.
Why it's wrong here
Global Accelerator works with TCP/UDP but does not route to microservices based on port within a single listener.
✗
Use an Application Load Balancer with path-based routing to direct traffic to separate microservices.
Why it's wrong here
ALB works at HTTP/HTTPS layer, not for binary TCP protocol.
✗
Use Amazon API Gateway with a custom authorizer to route requests to AWS Lambda functions.
Common exam trap: NAT rules depend on direction and matching traffic
NAT is not only about the public address. The inside/outside interface roles and the ACL or rule that matches traffic are just as important.
Detailed technical explanation
How to think about this question
NAT questions usually test address translation, overload/PAT behaviour, static mappings and whether the right traffic is being translated. Read the interface direction and address terms carefully.
KKey Concepts to Remember
Static NAT maps one inside address to one outside address.
PAT allows many inside hosts to share one public address using ports.
Inside local and inside global describe the private and translated addresses.
NAT ACLs identify traffic for translation, not always security filtering.
TExam Day Tips
→Identify inside and outside interfaces first.
→Check whether the scenario needs static NAT, dynamic NAT or PAT.
→Do not confuse NAT matching ACLs with normal packet-filtering intent.
Key takeaway
NAT direction and interface roles matter as much as the IP address mapping. Inside/outside designation controls which traffic is translated.
Real-world example
How this comes up in practice
A healthcare organisation deploys an application with a public-facing web tier and a private database tier. The database subnet has no public IP and only accepts connections from the web tier's security group. Questions like this test whether you can design cloud network isolation using VNets/VPCs, subnets, and security group rules.
What to study next
Got this wrong? Here's your next step.
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related SAP-C02 NAT questions on configuration and troubleshooting.
Design for New Solutions — This question tests Design for New Solutions — Static NAT maps one inside address to one outside address..
What is the correct answer to this question?
The correct answer is: Use a Network Load Balancer with TCP listener and route traffic based on destination port to different target groups. — Networking Load Balancer with TCP listener and target groups allows routing based on protocol without modifying clients. Option A (ALB) requires HTTP. Option C (API Gateway) requires REST. Option D (AWS Global Accelerator) uses anycast IP but still needs TCP routing.
What should I do if I get this SAP-C02 question wrong?
Review the four NAT address types (inside local, inside global, outside local, outside global), PAT port overload, and static vs dynamic NAT use cases. Then practise related SAP-C02 NAT questions on configuration and troubleshooting.
What is the key concept behind this question?
Static NAT maps one inside address to one outside address.
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Question Discussion
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