AWS IAM for beginners
A beginner’s guide to AWS IAM: users, groups, roles and policies, plus MFA and least privilege, explained with a simple S3 example.
To go beyond reading, I tried IAM myself. I started by turning on MFA for my account and avoiding the root user for everyday work. Then I created an IAM user and attached a read-only S3 policy to it. When I signed in as that user, I could list and download files from my bucket, but uploading a file was denied with an “access denied” message. At first this looked like an error, but it showed me exactly how least privilege works: the user can do only what the policy allows, and nothing more. I then opened the policy’s JSON and read it line by line, matching the Effect, Action and Resource fields to what I had seen. I also learned that when something fails in AWS, IAM permissions are often the first place to check. This matters for data engineering, because services like Glue and Athena need IAM roles to read data from S3, and a missing permission can stop a whole pipeline. From my AWS internship, I also saw that teams prefer roles over sharing access keys, because roles give temporary access and are safer. Overall, these small experiments helped me understand IAM much better than theory alone, and they gave me more confidence for the Cloud Practitioner exam.
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