Which solution will require the LEAST amount of effort?
Enable cross-account S3 replication for the bucket.
Create a pre-signed URL for the bucket and share it with other departments.
Set the S3 bucket policy to allow cross-account access to other departments.
Create IAM users for each of the departments and configure a read-only IAM policy.
Explanations:
Cross-account S3 replication is used for replicating objects from one S3 bucket to another across different accounts. While it allows for data sharing, it involves more setup and management overhead compared to directly allowing access through bucket policies.
Creating a pre-signed URL is a temporary solution that provides access to a specific object in the S3 bucket, not the entire bucket. This method can be cumbersome for ongoing access needs across multiple departments, as new URLs would need to be generated and shared each time access is required.
Setting the S3 bucket policy to allow cross-account access is the most efficient way to enable access for all other departments. It requires minimal effort to update the bucket policy and grants the necessary permissions without needing to create or manage additional IAM users or roles.
Creating IAM users for each department and configuring a read-only IAM policy would involve significant administrative overhead, as it requires creating and managing multiple IAM users and policies, which is not as efficient as using bucket policies for cross-account access.
I appraise that the answer is:
Set the S3 bucket policy to allow cross-account access to other departments.