AWS IAM Interview Questions: Policies, Roles, Permission Boundaries & SCPs

Identity and Access Management is one of the most common topics asked in AWS interviews. Whether someone is preparing for a cloud engineer, DevOps, security engineer, or solutions architect role, a solid understanding of IAM policies, roles, permission boundaries, SCPs, and authentication is essential. This blog provides a complete set of interview questions and answers explained in a simple and human-friendly manner. It is designed to help candidates speak confidently during interviews and gain real clarity on how IAM security controls actually work inside AWS.

IAM ensures that the right identity has the right access to the right resource. Many interviewers test practical understanding of how IAM controls access across accounts, applications, and users — especially when working with AWS Organizations. So let’s explore the most important questions.

Top AWS IAM Interview Questions & Answers

Question 1. What is AWS IAM and why is it important?

Answer: AWS IAM is a managed service that controls authentication and authorization for AWS services. It allows users, applications, and systems to securely access cloud resources using policies. IAM plays a crucial role in security because it ensures only trusted identities can perform permitted actions.

Question 2. What is the difference between authentication and authorization in IAM?

Answer: Authentication is about proving identity — like logging in using a password, MFA, or programmatic credentials.
Authorization defines what an identity is allowed to do — controlled through IAM policies and roles.

Example: A user can authenticate into AWS but may not be authorized to delete an S3 bucket.

Question 3. What are IAM policies and how do they work?

Answer: IAM policies are JSON documents that define allowed or denied actions for identities. An IAM policy contains four major elements:

AWS evaluates all policies attached to a user, group, or role to decide access.

Question 4. What types of IAM policies exist in AWS?

Answer:

• Identity-based policies – attached to users, groups, or roles
• Resource-based policies – added directly to a resource (like an S3 bucket policy)
• Permissions boundaries – maximum allowed access for a role or user
• Service control policies (SCPs) – organization-level restrictions that apply to accounts

Question 5. What is the priority of Allow and Deny in IAM?

Answer: Deny overrides everything. Even if multiple policies allow an action, a single Deny (explicit or from SCP) blocks access.

Question 6. What are IAM roles?

Answer: IAM roles are temporary identity credentials that trusted entities can assume. They are used instead of static long-term credentials.

Example use cases:

• EC2 instance accessing S3 without access keys
• Cross-account access via AWS Organizations
• Serverless authentication with Lambda functions

Roles ensure better security and reduce credential exposure.

Question 7. What is the difference between an IAM user and an IAM role?

Answer:

Roles are preferred for operational access because IAM users create credential management risks.

Question 8. What are permission boundaries?

Answer: Permission boundaries set the maximum allowed permissions for IAM users or roles. Even if a user policy allows access, the boundary will block actions outside its scope.

Think of it as:

“You can’t exceed this security fence even if another policy says Yes.”

Used heavily in enterprise environments where developers self-manage IAM roles.

Question 9. What are Service Control Policies (SCPs)?

Answer: Service control policies are organization-wide governance rules applied via AWS Organizations. SCPs limit what member accounts can do — even users with admin privileges.

Common use case examples:

• Restrict accounts from disabling CloudTrail
• Prevent IAM changes in production accounts
• Block creation of specific expensive services

SCPs ensure compliance and centralized control.

Question 10. How do permission boundaries differ from SCPs?

Answer:

Both require policies to Allow access — neither grants permissions on their own.

Question 11. What is a trust policy in IAM roles?

Answer: A trust policy defines which identities are allowed to assume the role. Without trust, a role can’t be used. It works with identity-based policies to establish mutual trust.

Example: EC2 service assumes a role based on a trust policy specifying “ec2.amazonaws.com”.

Question 12. What is cross-account access and how does IAM support it?

Answer: Cross-account access allows identities in one AWS account to access resources in another. It is achieved using:

• IAM roles with trust policies
• Resource-based policies (like bucket policies)

No access keys are shared, making it more secure for multi-account architecture.

Question 13. What are inline and managed IAM policies?

Answer:

Managed policies are recommended for large teams.

Question 14. How does IAM integrate with Multi-Factor Authentication?

Answer: MFA adds a second verification factor to authentication. IAM can enforce MFA conditions using policies, like:

"Condition": {"Bool": {"aws:MultiFactorAuthPresent": "true"}}

This is used for privileged administrative access.

Question 15. What are Access Advisor and IAM Access Analyzer?

Answer: These are IAM tools used to improve security:

• Access Advisor: Shows last-used services to remove unused permissions.
• Access Analyzer: Identifies resources exposed publicly or cross-account.

Conclusion

IAM is one of the most critical components in AWS security. Interviews often focus on how IAM controls authentication, policies, roles, permission boundaries, and SCPs. Rather than memorizing terms, practice explaining them in simple real-world language. Understanding policy evaluation, role assumptions, and multi-account restrictions will help you excel in cloud security-focused roles.

If you can confidently explain how IAM protects access across services and accounts, you are already ahead in your interview preparation.