DBS-C01 Management and Operations Practice Question
Network Topology
A DBA runs the IAM policy simulation above. The DBA can describe the DB instance but cannot modify it. What is the most likely cause?
⚠ Common exam trap
Many exam-takers assume a missing allow is the cause, but AWS IAM simulation results clearly distinguish between implicit deny (no policy allows) and explicit deny (a policy specifically denies), and the question's phrasing 'cannot modify' combined with the simulation context points to an explicit deny as the most likely cause.
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
✓
An IAM policy explicitly denies the rds:ModifyDBInstance action.
The simulation shows that the DBA can describe the DB instance but cannot modify it. Since the simulation evaluates all applicable IAM policies, an explicit deny for rds:ModifyDBInstance in any attached policy will override any allow and cause the modify action to fail. This is the most likely cause because explicit denies are evaluated first and cannot be overridden by other policies.
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 resource ARN in the simulation is incorrect.
Why it's wrong here
The ARN appears correct as it allowed DescribeDBInstances.
- ✓
An IAM policy explicitly denies the rds:ModifyDBInstance action.
Why this is correct
The evaluation result shows 'explicitDeny' for ModifyDBInstance.
- ✗
The DBA's IAM policy does not include an allow for rds:ModifyDBInstance.
Why it's wrong here
Missing allow would result in 'implicitDeny', not 'explicitDeny'.
- ✗
The DBA is not within the VPC where the DB instance resides.
Why it's wrong here
IAM simulation does not consider network location.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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