ALB Backend Encryption with HTTPS Target Group
A company uses an Application Load Balancer (ALB) to distribute traffic to EC2 instances. The security team wants to ensure that all traffic between the ALB and the instances is encrypted. Which configuration step is required?
Quick Answer
The correct answer is to configure the target group to use the HTTPS protocol and install SSL/TLS certificates on the EC2 instances. This ensures that the Application Load Balancer encrypts all backend traffic between itself and the instances by establishing a TLS handshake for every request, rather than sending data in plaintext over HTTP. On the AWS Certified SysOps Administrator Associate SOA-C02 exam, this scenario tests your understanding of the difference between client-facing encryption (configured on the listener) and backend encryption (configured on the target group). A common trap is confusing the listener’s HTTPS setting with the target group’s protocol—remember, the listener secures traffic from the client, while the target group secures traffic to the backend. To recall this, use the mnemonic: “Listener for the client, Target for the backend.”
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
✓
Configure the target group to use HTTPS protocol and install SSL/TLS certificates on the instances.
Configuring the target group to use the HTTPS protocol ensures that the ALB encrypts traffic to the instances using SSL/TLS. The instances must have valid certificates installed to terminate the HTTPS connection. Option A is incorrect because the ALB listener handles encryption between clients and the ALB, not between the ALB and instances. Option C is incorrect because placing instances in a private subnet and using a NAT gateway affects outbound internet access, not encryption between the ALB and instances. Option D is incorrect because a security group rule can allow only HTTPS traffic, but it does not enforce encryption; the traffic protocol must also be HTTPS.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Configure the ALB listener to use HTTPS with a security policy.
Why it's wrong here
An HTTPS listener encrypts only the client-to-ALB leg; the ALB-to-instance hop stays plaintext unless the target group is switched to HTTPS. It is tempting because listener configuration is the visible TLS setting, yet it terminates at the load balancer rather than protecting backend traffic.
- ✓
Configure the target group to use HTTPS protocol and install SSL/TLS certificates on the instances.
Why this is correct
The ALB-to-instance hop is encrypted only when the target group's protocol is HTTPS and the instances present valid certificates. Setting the target group to HTTPS satisfies the requirement, since the listener's own TLS termination covers only the client-to-ALB leg.
- ✗
Place the instances in a private subnet and use a NAT gateway for outbound traffic.
Why it's wrong here
Private subnets and NAT gateways govern outbound internet routing, not the protocol used between the ALB and its targets, so traffic remains unencrypted. It is tempting because private subnets are a standard hardening measure, but they address network exposure rather than transport-layer encryption.
- ✗
Create a security group rule that allows only HTTPS traffic from the ALB to the instances.
Why it's wrong here
A security group permitting HTTPS controls which ports reach the instances but does not encrypt traffic; the ALB still forwards plaintext HTTP unless the target group protocol is HTTPS. It is tempting because security groups are the usual tool for restricting ALB-to-instance access, which is a separate concern from transport encryption.
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1 more way this is tested on SOA-C02
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Variation 1. A company has a fleet of EC2 instances in an Auto Scaling group behind an Application Load Balancer. The security team requires that all traffic to the instances be encrypted in transit. Currently, the ALB terminates HTTPS and forwards HTTP to the instances. The security team wants to ensure that the traffic between the ALB and the instances is also encrypted. What should the SysOps administrator do to meet this requirement with minimal changes?
easy- A.Replace the ALB with a Network Load Balancer and use TLS termination on the instances.
- B.Place a CloudFront distribution in front of the ALB and use HTTPS for all origins.
- C.Set up a VPN connection between the ALB and the instances.
- ✓ D.Change the ALB listener to use HTTPS and configure the target group to use HTTPS with a self-signed certificate on the instances.
Why D: It encrypts traffic between the ALB and EC2 instances with minimal changes: you change the ALB listener to HTTPS and configure the target group to use HTTPS, using a self-signed certificate on the instances for encryption. Option A is incorrect because replacing the ALB with a Network Load Balancer is not minimal and adds complexity. Option B is incorrect because adding a CloudFront distribution introduces additional cost and overhead, not minimal. Option C is incorrect because setting up a VPN connection is overly complex and not necessary for this requirement.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This SOA-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 SOA-C02 exam.