DOP-C02 Configuration Management and IaC Practice Question
A developer wants to use AWS CloudFormation to create an Amazon RDS DB instance. The template includes a DB instance resource. Which property is required for the DB instance to be created successfully?
⚠ Common exam trap
Test-takers frequently assume MasterUsername and MasterUserPassword are always required because they are mandatory in the AWS Management Console wizard, but CloudFormation allows omitting them when the DB instance is created from a snapshot or as a read replica, making DBInstanceClass and Engine the only universally required properties.
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
✓
DBInstanceClass and Engine
In AWS CloudFormation, when creating an Amazon RDS DB instance using the AWS::RDS::DBInstance resource, the only truly required properties are DBInstanceClass (the compute and memory capacity) and Engine (the database engine, e.g., MySQL, PostgreSQL). These two properties are mandatory in the CloudFormation resource specification; without them, the template will fail validation. All other properties, such as AllocatedStorage, DBInstanceIdentifier, MasterUsername, and MasterUserPassword, have default behaviors or can be omitted under certain conditions (e.g., AllocatedStorage defaults to 20 GB for some engines, and MasterUsername/MasterUserPassword are not required if you use a snapshot or a source DB instance).
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
DBInstanceClass and Engine
Why this is correct
In CloudFormation's AWS::RDS::DBInstance resource, DBInstanceClass and Engine are mandatory properties for every instance. DBInstanceClass defines the instance's compute and memory capacity, while Engine specifies the database engine (e.g., mysql, postgres). Without these, the resource automatically fails validation because CloudFormation can't provision a database without a compute class and an engine type. This makes this pair the correct answer for the property required universally.
- ✗
AllocatedStorage
Why it's wrong here
AllocatedStorage is required for some engines, but it is not universally mandatory. For Amazon Aurora, storage automatically scales and AllocatedStorage cannot even be specified on the instance; it is managed by the cluster. Additionally, when restoring a DB instance from a snapshot, you omit this property. Thus, while often needed, it does not qualify as a required property for all DB instance resources.
- ✗
DBInstanceIdentifier
Why it's wrong here
DBInstanceIdentifier is an optional property because it is simply a user-defined name for the instance. If you omit it, CloudFormation or RDS will automatically generate a unique identifier. Whether or not you provide it has no bearing on the instance's configuration or provisioning, so it is not a required property. This eliminates it as the correct answer.
- ✗
MasterUsername and MasterUserPassword
Why it's wrong here
MasterUsername and MasterUserPassword are required only when provisioning a brand-new DB instance directly. In Aurora, master credentials belong to the preceding DBCluster resource, so the instance resource does not require them; similarly, when restoring from a snapshot, the existing user accounts carry over, making these properties unnecessary. Since the question asks for a property that is always required, this conditionally required pair is incorrect, unlike DBInstanceClass and Engine.
Quick reference
AWS S3 Storage Class Comparison
| Storage Class | Min Duration | Retrieval | Use Case |
|---|---|---|---|
| S3 Standard | None | Immediate | Frequently accessed data |
| S3 Standard-IA | 30 days | Immediate | Infrequent access, rapid retrieval |
| S3 One Zone-IA | 30 days | Immediate | Non-critical infrequent data |
| S3 Intelligent-Tiering | None | Immediate–hours | Unknown or changing access patterns |
| S3 Glacier Instant | 90 days | Milliseconds | Archive with instant retrieval |
| S3 Glacier Flexible | 90 days | Minutes–hours | Archive, flexible retrieval |
| S3 Glacier Deep Archive | 180 days | Hours | Long-term compliance archive |
Go deeper
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This DOP-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 DOP-C02 exam.