Which AWS service is always provided at no charge?
Amazon S3
AWS Identity and Access Management (IAM)
Elastic Load Balancers
AWS WAF
Explanations:
Amazon S3 has a free tier, but usage beyond the free tier incurs charges.
AWS Identity and Access Management (IAM) is always free for all users regardless of usage.
Elastic Load Balancers are charged based on usage and are not free.
AWS WAF (Web Application Firewall) incurs charges based on the number of rules and requests.
In my experience, the answer is:
AWS Identity and Access Management (IAM)