A real case: scalability blocked by poor IAM usage
In 2023, a fintech company undergoing AWS expansion faced a critical limitation: its access model based on IAM Users was not aligned with modern federated identity practices or automation. Each new microservice required manual permissions, and credential rotation was an operational pain. The security team audited the environment and discovered that several IAM Users had been accumulating excessive privileges for months. None of those accounts used MFA or centralized activity tracking.
This situation exposes a common confusion: treating IAM Users and Roles as equivalent or interchangeable. In reality, their purpose, scope, and operational security are different. Understanding those differences helps reduce risk, improve elasticity, and comply with internal controls.
What is an IAM User and what should it (not) be used for
An IAM User represents a persistent identity in AWS. It has credentials assigned directly: username, password, and access keys. This makes it useful in cases where a specific person or system needs explicit and durable access to the AWS environment, such as a break-glass account in emergencies.
However, widespread use of IAM Users creates several problems:
- Complex credential management: Periodic rotation of manual keys is difficult to audit and maintain, especially in production environments.
- Increased attack surface: Fixed credentials expose higher risk in case of compromise, especially if MFA is not mandatory.
A typical mistake seen in mid-sized companies is creating an IAM User for each automated application. This even leads to storing access keys in pipelines or repositories, creating technical debt and systemic risk. The correct approach would be to use assumable Roles, but this difference is not always known from the start.
IAM Roles: temporary, controlled, and auditable identities
An IAM Role in AWS represents a set of permissions that can be temporarily assumed by human identities, services, or external accounts. Its main advantage is that it has no credentials of its own: it is assumed via a controlled, verified, and auditable process.
Example: a container in ECS can assume a Role named app-orders-role that grants it only permissions to write to a specific SQS queue. Temporary credentials are automatically provided by the AWS runtime (STS), without needing to embed keys in code or storage.
- Controlled assumption: You define who can assume which Role under what conditions, using trust policies.
- Limited duration: The generated credentials expire in minutes, reducing the risk of misuse if leaked.
In mature enterprise environments, IAM Users tend to be phased out in favor of Roles, especially when combined with federated identity (such as SAML or AWS SSO). Traceability is better, compliance becomes easier, and automation is cleaner.
Anti-pattern: using IAM Users in automated systems
It is common — especially in startups or early migrations — for developers to create IAM Users for each automated component. They seem like a quick fix: generate access keys, store them in variables, and done.
But this approach does not scale well and compromises security:
- Ineffective rotation: Access keys remain forgotten for months. If someone accidentally shares a key in a repository, there is no automatic expiration.
- Lack of segregation: Since permissions are tied to a fixed account, they are often copied across services. This breaks the principle of least privilege.
An audit conducted in a logistics company found more than 20 active keys without rotation for 180 days, used by different microservices. Some had administrator permissions. The forced remediation caused outages in undocumented services.
How to do it in practice: transitioning from IAM Users to Roles
Making this change in an organization requires assessment and careful planning. It is not about arbitrarily deleting IAM Users, but about replacing them in a controlled manner.
Recommended steps:
- Inventory existing IAM Users: Identify active keys, last usage dates, and the roles they play in the ecosystem.
- Classify by usage type: Humans vs systems. For humans, evaluate migration to AWS Identity Center. For systems, map each usage to a component and define equivalent Roles.
- Create Roles with minimal required policies: Implement least privilege policies using previous access log analysis (Access Analyzer or CloudTrail).
- Update pipelines and infrastructure: Remove hardcoded credentials, configure IAM Roles in EC2, ECS, Lambda, or CI/CD.
- Audit and delete old IAM User keys: Only after the transition has been fully validated.
This process, when well executed, strengthens the security posture without disrupting operations.
Recommendations for enterprise environments
IAM User and IAM Role are not interchangeable. In companies, it is recommended to strictly limit IAM Users to specific human identities that cannot be federated and to break-glass accounts with reinforced control. Standard operational use should focus on Roles—both for automated services and for internal users accessing via SSO or federation.
Making this operational distinction from the design stage prevents many common errors: accumulated privileges, leaked permanent keys, and lack of traceability. Organizations that have migrated to a Role-based model not only reduce risks but simplify audits, onboarding, and regulatory compliance. Implementing it requires effort, but it is a critical step toward a secure and maintainable cloud architecture.
Interested in Cloud Security?
Technical analysis, hands-on labs and real-world cloud security insights.