IAM Policy Explicit Deny: Why It Overrides Any Allow
This SAP-C02 practice question tests your understanding of design solutions for organizational complexity. 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.
An administrator attached the above IAM policy to a group of developers. A developer tries to launch a t3.medium EC2 instance and receives an 'AccessDenied' error. What is the MOST likely reason?
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.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The policy denies all instance types except t3.micro and t3.small.
The IAM policy includes a Deny statement that explicitly denies ec2:RunInstances for any instance type that is not t3.micro or t3.small. Since the developer is attempting to launch a t3.medium instance, which is not listed in the allowed types, the Deny statement matches and overrides any Allow, resulting in an AccessDenied error. This is the most likely reason because explicit Deny always takes precedence over Allow in IAM policy evaluation logic.
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 policy denies all instance types except t3.micro and t3.small.
Why this is correct
The condition denies if the instance type is not in the list.
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 policy has a syntax error that causes all actions to be denied.
Why it's wrong here
The policy syntax is valid.
✗
The policy does not explicitly allow ec2:RunInstances.
Why it's wrong here
An explicit deny overrides any allow, so the allow is not needed here.
✗
The policy requires a specific Amazon Machine Image (AMI) that the developer is not using.
Why it's wrong here
The policy does not reference AMIs.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates may overlook the explicit Deny statement and assume the error is due to a missing Allow, but AWS IAM requires both an Allow and no matching Deny for the action to succeed, and the Deny here is the direct cause of the failure.
Detailed technical explanation
How to think about this question
IAM policy evaluation uses an explicit Deny override model: if any statement in the policy explicitly denies an action, that Deny is applied regardless of any Allow statements. The condition in the Deny uses ec2:InstanceType with a ForAllValues:StringNotEquals operator, which denies the action if the requested instance type is not in the specified list. This is a common pattern to restrict instance families while still allowing specific sizes, and it demonstrates how IAM conditions can be used to enforce resource-level restrictions beyond simple action permissions.
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.
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.
Design Solutions for Organizational Complexity — This question tests Design Solutions for Organizational Complexity — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The policy denies all instance types except t3.micro and t3.small. — The IAM policy includes a Deny statement that explicitly denies ec2:RunInstances for any instance type that is not t3.micro or t3.small. Since the developer is attempting to launch a t3.medium instance, which is not listed in the allowed types, the Deny statement matches and overrides any Allow, resulting in an AccessDenied error. This is the most likely reason because explicit Deny always takes precedence over Allow in IAM policy evaluation logic.
What should I do if I get this SAP-C02 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.
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Question Discussion
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