IAM User S3 permission and Bucket permission in S3 which one will execute first?

Question

I have an IAM user and i have given S3 full access to specific user, also i am giving some access permissions in S3 bucket separately, i want to know which one will execute first. either it will give full access to my user according to IAM or it will work according to the S3 permission

Answer 1

It will use both of the permissions.

First, any Deny permissions will be evaluated (on the IAM User, any IAM Group they belong to, and in the Bucket Policy). If the request matches a Deny policy, then the request is denied.

Next, all Allow permissions are evaluated. If the request matches an Allow policy, then the request is allowed.

So, in the absence of any Deny policies, a request will be permitted as long as any permission grants the access.