AWS IAM Explained: Users, Roles, Policies, and Least Privilege (opens in new tab)

AWS IAM (Identity and Access Management) is the authorization layer for everything in AWS. Every API call — whether from the console, CLI, an EC2 instance, or a Lambda function — is evaluated against IAM policy. Get it wrong and you either lock out legitimate services or leave your infrastructure open to lateral movement. Despite its importance, IAM is where most teams accumulate the most technical debt, usually in the form of overly broad policies that were "temporary" and became permanent. ...