- A
Place all tiers in public subnets and use security groups to restrict traffic.
Why wrong: This exposes app and database tiers to the internet, which is not isolated.
- B
Place the web tier in a public subnet with an internet gateway, and the app and database tiers in private subnets. Use separate security groups for each tier, allowing only necessary traffic.
This ensures isolation and encryption can be applied at the application layer.
- C
Place the web and app tiers in public subnets and the database in a private subnet.
Why wrong: The app tier in a public subnet is exposed and unnecessary.
- D
Place all tiers in private subnets and use a single security group to allow traffic between them.
Why wrong: A single security group does not provide fine-grained isolation between tiers.
Quick Answer
The correct architecture uses separate security groups for each tier with security group chaining, where the web tier sits in a public subnet with an Internet Gateway and the app and database tiers reside in private subnets. This design enforces least-privilege by allowing the app tier security group to reference the web tier security group as its only inbound source, and the database tier security group to reference only the app tier security group, ensuring encrypted traffic flows only along authorized paths. On the AWS Certified Security Specialty SCS-C02 exam, multi-tier security group chaining tests your ability to implement network segmentation without relying on network ACLs or NAT instances—a common trap is using IP-based rules instead of security group references, which breaks dynamic scaling and fails the isolation requirement. Remember the memory tip: “Chain the groups, not the IPs” to avoid over-permissive rules and maintain encryption enforcement between tiers.
SCS-C02 Infrastructure Security Practice Question
This SCS-C02 practice question tests your understanding of infrastructure security. 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 designing a multi-tier web application on AWS. The web tier must be accessible from the internet, but the application and database tiers must be isolated. The security team requires that all traffic between tiers be encrypted and that the application tier can only be accessed by the web tier. Which architecture should be used?
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
Place the web tier in a public subnet with an internet gateway, and the app and database tiers in private subnets. Use separate security groups for each tier, allowing only necessary traffic.
Option B is correct because it places the web tier in a public subnet with an Internet Gateway (IGW) for internet-facing access, while the application and database tiers reside in private subnets with no direct internet path. Separate security groups enforce least-privilege: the web tier security group allows inbound HTTP/HTTPS (ports 80/443) from 0.0.0.0/0, the app tier security group allows inbound traffic only from the web tier security group (using a security group reference), and the database tier security group allows inbound traffic only from the app tier security group. This ensures encryption (e.g., TLS for web-to-app, and database-native encryption like TLS or AWS RDS encryption in transit) and complete isolation of the internal tiers.
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.
- ✗
Place all tiers in public subnets and use security groups to restrict traffic.
Why it's wrong here
This exposes app and database tiers to the internet, which is not isolated.
- ✓
Place the web tier in a public subnet with an internet gateway, and the app and database tiers in private subnets. Use separate security groups for each tier, allowing only necessary traffic.
Why this is correct
This ensures isolation and encryption can be applied at the application layer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Place the web and app tiers in public subnets and the database in a private subnet.
Why it's wrong here
The app tier in a public subnet is exposed and unnecessary.
- ✗
Place all tiers in private subnets and use a single security group to allow traffic between them.
Why it's wrong here
A single security group does not provide fine-grained isolation between tiers.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates assume security groups alone can isolate tiers in public subnets, ignoring that public subnets have a direct route to the internet via the IGW, which bypasses security group restrictions for inbound traffic from the internet.
Detailed technical explanation
How to think about this question
Under the hood, security group rules using security group IDs as sources (e.g., sg-xxxxx) create stateful, instance-level firewalls that track connection state, so return traffic is automatically allowed. In this architecture, the web tier can initiate outbound connections to the app tier, but the app tier cannot initiate connections back to the web tier unless explicitly allowed. For encryption, TLS termination can occur on an Application Load Balancer (ALB) in the public subnet, while the app tier uses mutual TLS (mTLS) or AWS Certificate Manager (ACM) for internal encryption; database connections should use TLS with certificates (e.g., for RDS PostgreSQL or MySQL). A real-world scenario is a PCI-DSS compliant application where the database must be in a private subnet with no direct internet access, and all inter-tier traffic must be encrypted at the application layer.
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 media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this SCS-C02 question test?
Infrastructure Security — This question tests Infrastructure Security — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Place the web tier in a public subnet with an internet gateway, and the app and database tiers in private subnets. Use separate security groups for each tier, allowing only necessary traffic. — Option B is correct because it places the web tier in a public subnet with an Internet Gateway (IGW) for internet-facing access, while the application and database tiers reside in private subnets with no direct internet path. Separate security groups enforce least-privilege: the web tier security group allows inbound HTTP/HTTPS (ports 80/443) from 0.0.0.0/0, the app tier security group allows inbound traffic only from the web tier security group (using a security group reference), and the database tier security group allows inbound traffic only from the app tier security group. This ensures encryption (e.g., TLS for web-to-app, and database-native encryption like TLS or AWS RDS encryption in transit) and complete isolation of the internal tiers.
What should I do if I get this SCS-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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Same concept, more angles
1 more ways this is tested on SCS-C02
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A company is designing a multi-tier web application. The web servers must be accessible from the internet, but the application servers must only be accessible from the web servers. Which AWS feature should be used to meet these requirements?
easy- ✓ A.Use security groups with rules that allow inbound traffic to the web servers from the internet, and allow inbound traffic to the application servers only from the web server security group.
- B.Use a VPC peering connection between the web tier and application tier subnets.
- C.Use network ACLs to allow inbound traffic to the web tier from the internet and to the application tier only from the web tier.
- D.Use a VPN connection to isolate the application tier from the web tier.
Why A: The correct answer is B because security groups act as a virtual firewall for instances, and you can reference another security group as a source. Option A is wrong because a NACL is stateless and applied at the subnet level; it can be used but security groups are simpler for instance-level control. Option C is wrong because a VPC peering is for connecting VPCs. Option D is wrong because a VPN connection is for hybrid connectivity.
Last reviewed: Jun 11, 2026
This SCS-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 SCS-C02 exam.
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