The answer is to launch the ECS tasks in the same private subnet as the RDS instance. This is correct because ECS tasks using Fargate must reside within the same VPC and subnet as the database to ensure direct network connectivity, as private subnets have no internet gateway and rely on internal routing. On the AWS Certified Solutions Architect Professional SAP-C02 exam, this scenario tests your understanding of VPC networking fundamentals and the principle that containers in a public subnet cannot reach resources in a private subnet without a bastion host or VPC peering, making the direct placement the simplest and most secure solution. A common trap is assuming a NAT gateway or VPN is needed, but those are for outbound internet access or hybrid connectivity, not for internal subnet-to-subnet communication. Memory tip: keep your database and compute in the same private subnet to avoid unnecessary routing complexity.
SAP-C02 Continuous Improvement for Existing Solutions Practice Question
This SAP-C02 practice question tests your understanding of continuous improvement for existing solutions. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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 runs a containerized application on Amazon ECS with Fargate. The application needs to access an Amazon RDS database that is in a private subnet. The ECS tasks are launched in a public subnet. How should they configure network access?
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Launch the ECS tasks in the same private subnet as the RDS instance.
Option D is correct because ECS tasks should be launched in the same VPC and security group as the database, or use VPC peering/transit gateway. Option A is wrong because NAT gateway is for outbound. Option B is wrong because public subnet tasks cannot directly access private RDS without proper routing. Option C is wrong because VPN is overkill.
Key principle: Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Launch the ECS tasks in the same private subnet as the RDS instance.
Why this is correct
Tasks in the same subnet can communicate via security groups.
Place the ECS tasks in a public subnet and use a NAT gateway to route traffic to the database.
Why it's wrong here
NATgateway is for outbound internet, not inbound to private subnet.
✗
Set up a VPN connection between the ECS tasks and the database.
Why it's wrong here
VPN is unnecessary; same VPC connectivity is sufficient.
✗
Use an Application Load Balancer to route traffic to the database.
Why it's wrong here
ALB is for HTTP/HTTPS traffic, not database connections.
Common exam traps
Common exam trap: usable hosts are not the same as total addresses
Subnetting questions often tempt you into counting all addresses. In normal IPv4 subnets, the network and broadcast addresses are not usable host addresses.
Detailed technical explanation
How to think about this question
Subnetting questions test whether you can identify the network, broadcast address, usable range, mask and correct subnet. Slow down enough to calculate the block size correctly.
KKey Concepts to Remember
CIDR notation defines the prefix length.
Block size helps identify subnet boundaries.
Network and broadcast addresses are not usable hosts in normal IPv4 subnets.
The required host count determines the smallest suitable subnet.
TExam Day Tips
→Write the block size before choosing the subnet.
→Check whether the question asks for hosts, subnets or a specific address range.
→Do not confuse /24, /25, /26 and /27 host counts.
Key takeaway
Count usable hosts — not total addresses — and remember that the network and broadcast addresses are not available to hosts in standard IPv4 subnets.
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.
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related SAP-C02 subnetting questions on CIDR, address ranges, and subnet selection.
Continuous Improvement for Existing Solutions — This question tests Continuous Improvement for Existing Solutions — CIDR notation defines the prefix length..
What is the correct answer to this question?
The correct answer is: Launch the ECS tasks in the same private subnet as the RDS instance. — Option D is correct because ECS tasks should be launched in the same VPC and security group as the database, or use VPC peering/transit gateway. Option A is wrong because NAT gateway is for outbound. Option B is wrong because public subnet tasks cannot directly access private RDS without proper routing. Option C is wrong because VPN is overkill.
What should I do if I get this SAP-C02 question wrong?
Review block sizes, usable host formulas (2^n − 2), and how to find network and broadcast addresses for /24 through /30. Then practise related SAP-C02 subnetting questions on CIDR, address ranges, and subnet selection.
What is the key concept behind this question?
CIDR notation defines the prefix length.
About these practice questions
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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 has deployed a web application on Amazon ECS with Fargate. The application needs to access an Amazon RDS database. The security team mandates that the database must not be publicly accessible. What is the best way to securely connect the ECS tasks to the RDS database?
easy
A.Use a NAT gateway to route traffic from ECS tasks to RDS.
B.Attach an internet gateway to the VPC and route through it.
C.Enable public accessibility on the RDS instance and restrict access to the ECS task public IP.
✓ D.Place the ECS tasks and RDS instance in the same VPC, and configure security groups to allow traffic on the database port.
Why D: Option A is correct because placing ECS tasks and RDS in the same VPC allows private communication via security groups. Option B is incorrect because NAT gateway is for outbound internet access. Option C is incorrect because a public endpoint would violate the security requirement. Option D is incorrect because an internet gateway is not needed for private communication.
Last reviewed: Jun 20, 2026
Question Discussion
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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.
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