- A
Attach an internet gateway to the VPC and route the private subnet's traffic to it.
Why wrong: This would make the private subnet public, which is not desired.
- B
Attach a NAT gateway to the private subnet and route traffic through it.
Why wrong: NAT gateways are for allowing private instances to access the internet, not for inbound access.
- C
Configure a network ACL on the private subnet to allow inbound traffic from the public subnet CIDR.
Why wrong: Network ACLs are stateless and allow traffic based on IP, but using CIDR may be too broad if there are other hosts in the public subnet.
- D
Create a security group for the RDS instances that allows inbound traffic from the security group attached to the application servers.
Security groups can reference other security groups, allowing traffic only from instances with that security group.
Quick Answer
The correct answer is to create a security group for the RDS instances that allows inbound traffic from the security group attached to the application servers. This configuration works because security groups are stateful and support referencing other security groups as a source, enabling you to restrict RDS access to a specific security group rather than relying on static IP addresses. On the AWS Certified SysOps Administrator Associate SOA-C02 exam, this scenario tests your understanding of how to secure RDS databases in private subnets using security groups, a common pattern for isolating database tiers. A frequent trap is choosing a CIDR-based rule for the application server’s subnet, which would still allow any resource in that subnet—including compromised instances—to reach the database. The key insight is that security group referencing dynamically adapts to scaling events or IP changes, making it more secure and flexible. Memory tip: think of it as “group-to-group, not IP-to-group” for dynamic database access control.
SOA-C02 Security and Compliance Practice Question
This SOA-C02 practice question tests your understanding of security and compliance. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 has a VPC with public and private subnets. The private subnets contain RDS databases that should not be accessible from the internet. Which configuration ensures that the databases are only accessible from the application servers in the public subnets?
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
Create a security group for the RDS instances that allows inbound traffic from the security group attached to the application servers.
Option D is correct because security groups act as a virtual firewall at the instance level, and you can reference another security group as a source. By creating a security group for the RDS instances that allows inbound traffic from the security group attached to the application servers, you ensure that only those application servers (regardless of their IP addresses) can reach the databases. This approach is more dynamic and secure than using CIDR-based rules, as it automatically accommodates changes in the application servers' IP addresses or scaling events.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Attach an internet gateway to the VPC and route the private subnet's traffic to it.
Why it's wrong here
This would make the private subnet public, which is not desired.
- ✗
Attach a NAT gateway to the private subnet and route traffic through it.
Why it's wrong here
NAT gateways are for allowing private instances to access the internet, not for inbound access.
- ✗
Configure a network ACL on the private subnet to allow inbound traffic from the public subnet CIDR.
Why it's wrong here
Network ACLs are stateless and allow traffic based on IP, but using CIDR may be too broad if there are other hosts in the public subnet.
- ✓
Create a security group for the RDS instances that allows inbound traffic from the security group attached to the application servers.
Why this is correct
Security groups can reference other security groups, allowing traffic only from instances with that security group.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse security groups with network ACLs, assuming that a network ACL rule allowing inbound traffic from the public subnet CIDR is sufficient, but they overlook that network ACLs are stateless and do not provide the same granular, instance-level control as security groups, nor do they automatically adapt to changes in application server IPs.
Detailed technical explanation
How to think about this question
Security group rules are stateful, meaning that if you allow inbound traffic from a source security group, the return traffic is automatically allowed regardless of outbound rules. When you reference a security group as a source, AWS evaluates the private IP addresses of all instances associated with that source security group, making it ideal for multi-tier architectures where application servers scale dynamically. In contrast, network ACLs are stateless and require separate inbound and outbound rules, and they operate at the subnet level, not the instance level, which can lead to overly permissive or complex configurations.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A company's IT admin needs to give a contractor read-only access to production logs without sharing account credentials. Using role-based access control (RBAC) and temporary scoped permissions — not a permanent shared password — is the correct pattern. Questions like this test whether you can apply least-privilege access across cloud identity services.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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Security and Compliance — study guide chapter
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Security and Compliance practice questions
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FAQ
Questions learners often ask
What does this SOA-C02 question test?
Security and Compliance — This question tests Security and Compliance — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Create a security group for the RDS instances that allows inbound traffic from the security group attached to the application servers. — Option D is correct because security groups act as a virtual firewall at the instance level, and you can reference another security group as a source. By creating a security group for the RDS instances that allows inbound traffic from the security group attached to the application servers, you ensure that only those application servers (regardless of their IP addresses) can reach the databases. This approach is more dynamic and secure than using CIDR-based rules, as it automatically accommodates changes in the application servers' IP addresses or scaling events.
What should I do if I get this SOA-C02 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
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Last reviewed: Jun 24, 2026
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.
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