Courseiva
← DBS-C01
Full test
Question 1,285 of 1,730
Deployment and Migration →hardMultiple ChoiceObjective-mapped

DBS-C01 Deployment and Migration Practice Question

This DBS-C01 practice question tests your understanding of deployment and migration. 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.

Exhibit

Refer to the exhibit.

CloudFormation template snippet:

Resources:
  MyRDSInstance:
    Type: AWS::RDS::DBInstance
    Properties:
      DBInstanceClass: db.t3.medium
      Engine: MySQL
      MultiAZ: true
      DBSubnetGroupName: !Ref MyDBSubnetGroup
      VPCSecurityGroups:
        - !Ref MyDBSecurityGroup
      StorageType: gp2
      AllocatedStorage: 100
      BackupRetentionPeriod: 7
      DeletionProtection: true

  MyDBSecurityGroup:
    Type: AWS::EC2::SecurityGroup
    Properties:
      GroupDescription: Security group for RDS
      VpcId: !Ref MyVPC
      SecurityGroupIngress:
        - IpProtocol: tcp
          FromPort: 3306
          ToPort: 3306
          CidrIp: 10.0.0.0/16

  MyDBSubnetGroup:
    Type: AWS::RDS::DBSubnetGroup
    Properties:
      DBSubnetGroupDescription: Subnet group for RDS
      SubnetIds:
        - subnet-12345678
        - subnet-87654321

  MyEC2Instance:
    Type: AWS::EC2::Instance
    Properties:
      InstanceType: t2.micro
      ImageId: ami-0abcdef1234567890
      SecurityGroupIds:
        - !Ref MyEC2SecurityGroup
      SubnetId: subnet-12345678

  MyEC2SecurityGroup:
    Type: AWS::EC2::SecurityGroup
    Properties:
      GroupDescription: Security group for EC2
      VpcId: !Ref MyVPC
      SecurityGroupIngress:
        - IpProtocol: tcp
          FromPort: 3306
          ToPort: 3306
          CidrIp: 0.0.0.0/0
        - IpProtocol: tcp
          FromPort: 22
          ToPort: 22
          CidrIp: 0.0.0.0/0

Refer to the exhibit. A developer deploys this CloudFormation template. An application on the EC2 instance cannot connect to the RDS MySQL database. What is the MOST likely cause?

Clue words in this question

Noticing these words before you look at the options changes how you read each choice.

  • Clue: "most likely"

    Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.

Exhibit

Refer to the exhibit.

CloudFormation template snippet:

Resources:
  MyRDSInstance:
    Type: AWS::RDS::DBInstance
    Properties:
      DBInstanceClass: db.t3.medium
      Engine: MySQL
      MultiAZ: true
      DBSubnetGroupName: !Ref MyDBSubnetGroup
      VPCSecurityGroups:
        - !Ref MyDBSecurityGroup
      StorageType: gp2
      AllocatedStorage: 100
      BackupRetentionPeriod: 7
      DeletionProtection: true

  MyDBSecurityGroup:
    Type: AWS::EC2::SecurityGroup
    Properties:
      GroupDescription: Security group for RDS
      VpcId: !Ref MyVPC
      SecurityGroupIngress:
        - IpProtocol: tcp
          FromPort: 3306
          ToPort: 3306
          CidrIp: 10.0.0.0/16

  MyDBSubnetGroup:
    Type: AWS::RDS::DBSubnetGroup
    Properties:
      DBSubnetGroupDescription: Subnet group for RDS
      SubnetIds:
        - subnet-12345678
        - subnet-87654321

  MyEC2Instance:
    Type: AWS::EC2::Instance
    Properties:
      InstanceType: t2.micro
      ImageId: ami-0abcdef1234567890
      SecurityGroupIds:
        - !Ref MyEC2SecurityGroup
      SubnetId: subnet-12345678

  MyEC2SecurityGroup:
    Type: AWS::EC2::SecurityGroup
    Properties:
      GroupDescription: Security group for EC2
      VpcId: !Ref MyVPC
      SecurityGroupIngress:
        - IpProtocol: tcp
          FromPort: 3306
          ToPort: 3306
          CidrIp: 0.0.0.0/0
        - IpProtocol: tcp
          FromPort: 22
          ToPort: 22
          CidrIp: 0.0.0.0/0

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

✓

The EC2 security group allows inbound MySQL from 0.0.0.0/0 but the RDS security group only allows traffic from the VPC CIDR, which does not include the EC2 security group.

Option A is correct because the RDS security group only allows inbound MySQL traffic from the VPC CIDR (e.g., 10.0.0.0/16), but the EC2 instance's security group is not referenced. Since the EC2 instance's private IP may fall outside that CIDR (e.g., if it uses a different subnet or a public IP), the RDS security group blocks the connection. Security group rules must explicitly reference the EC2 security group ID to allow traffic from that specific instance, not just the VPC CIDR.

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.

  • ✓

    The EC2 security group allows inbound MySQL from 0.0.0.0/0 but the RDS security group only allows traffic from the VPC CIDR, which does not include the EC2 security group.

    Why this is correct

    RDS SG should allow traffic from EC2 SG, not just VPC CIDR.

    Clue confirmation

    The clue word "most likely" in the question point toward this answer.

    Related concept

    Read the scenario before looking for a memorised answer.

  • ✗

    The RDS instance has encryption enabled, preventing access from EC2.

    Why it's wrong here

    Encryption does not block network connectivity.

  • ✗

    The RDS instance has DeletionProtection enabled, which blocks connections.

    Why it's wrong here

    DeletionProtection prevents deletion, not connections.

  • ✗

    The EC2 instance is in a different Availability Zone than the RDS instance.

    Why it's wrong here

    Multi-AZ does not prevent connectivity across AZs.

Common exam traps

Common exam trap: answer the scenario, not the keyword

The trap here is that candidates assume a VPC CIDR rule in the RDS security group will automatically cover all EC2 instances in the VPC, but they overlook that the EC2 instance's private IP might be outside that CIDR (e.g., due to subnet allocation or NAT) or that security group referencing is required for proper traffic flow.

Detailed technical explanation

How to think about this question

Security groups are stateful and evaluate rules based on the source (CIDR or security group ID). When an RDS security group specifies a VPC CIDR as the source, it only allows traffic from IPs within that range. However, EC2 instances may use private IPs from a different subnet or a public IP (if in a public subnet), which may not match the VPC CIDR. The correct approach is to reference the EC2 security group ID in the RDS security group's inbound rule, allowing traffic from any instance associated with that security group, regardless of IP. This is a common pattern for multi-tier applications.

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.

Visual reference

192.168.1.0 /24 256 addresses (254 usable) 192.168.1.0 /25 Subnet A 128 addr (126 usable) 192.168.1.128 /25 Subnet B 128 addr (126 usable) Borrowing 1 bit from host portion creates 2 subnets (/25)

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.

Related practice questions

Related DBS-C01 practice-question pages

Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.

Workload-Specific Database Design practice questions

Practise DBS-C01 questions linked to Workload-Specific Database Design.

Deployment and Migration practice questions

Practise DBS-C01 questions linked to Deployment and Migration.

Management and Operations practice questions

Practise DBS-C01 questions linked to Management and Operations.

Monitoring and Troubleshooting practice questions

Practise DBS-C01 questions linked to Monitoring and Troubleshooting.

Database Security practice questions

Practise DBS-C01 questions linked to Database Security.

DBS-C01 fundamentals practice questions

Practise DBS-C01 questions linked to DBS-C01 fundamentals.

DBS-C01 scenario practice questions

Practise DBS-C01 questions linked to DBS-C01 scenario.

DBS-C01 troubleshooting practice questions

Practise DBS-C01 questions linked to DBS-C01 troubleshooting.

Practice this exam

Start a free DBS-C01 practice session

Short sessions build daily habit. Longer sessions build exam-day stamina. Try a timed session to simulate real conditions.

10 questions20 questions30 questions50 questionsTimed 30
DBS-C01 practice-test guide →Study guide →Browse all practice tests

FAQ

Questions learners often ask

What does this DBS-C01 question test?

Deployment and Migration — This question tests Deployment and Migration — Read the scenario before looking for a memorised answer..

What is the correct answer to this question?

The correct answer is: The EC2 security group allows inbound MySQL from 0.0.0.0/0 but the RDS security group only allows traffic from the VPC CIDR, which does not include the EC2 security group. — Option A is correct because the RDS security group only allows inbound MySQL traffic from the VPC CIDR (e.g., 10.0.0.0/16), but the EC2 instance's security group is not referenced. Since the EC2 instance's private IP may fall outside that CIDR (e.g., if it uses a different subnet or a public IP), the RDS security group blocks the connection. Security group rules must explicitly reference the EC2 security group ID to allow traffic from that specific instance, not just the VPC CIDR.

What should I do if I get this DBS-C01 question wrong?

Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.

Are there clue words in this question I should notice?

Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.

What is the key concept behind this question?

Read the scenario before looking for a memorised answer.

About these practice questions

Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →

How Courseiva writes practice questions · Editorial policy

Keep practising

More DBS-C01 practice questions

Browse all DBS-C01 questions →

Last reviewed: Jul 4, 2026

Question Discussion

Share a tip, memory trick, or ask about the reasoning behind this question. Do not post real exam questions, leaked content, braindumps, or copyrighted exam material. Comments are moderated and may be removed without notice.

Loading comments…

Sign in to join the discussion.

This DBS-C01 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 DBS-C01 exam.