AWS CloudTrail is a web service that records AWS API calls for your account and delivers log files to you. The recorded information includes the identity of the API caller, the time of the API call, the source IP address of the API caller, the request parameters, and the response elements returned by the AWS service.
With CloudTrail, you can get a history of AWS API calls for your account, including API calls made via the AWS Management Console, AWS SDKs, command line tools, and higher-level AWS services (such as AWS CloudFormation). The AWS API call history produced by CloudTrail enables security analysis, resource change tracking, and compliance auditing."
CloudTrail is a web service that tracks the history of AWS API calls for your account, including various services such as the AWS Management Console and various SDKs. This information is stored in S3 as log files. I don't think there is any performance impact, given the structure of AWS itself.