Comprehensive Detailed Step by Step Explanation with All AWS Developer References:

To redact PII from S3 objects before they are accessed by the analytics service, the most efficient solution is to use S3 Object Lambda. S3 Object Lambda allows you to add your own code (Lambda function) to process and transform data when it is retrieved from Amazon S3. You can attach a Lambda function to an S3 Object Lambda Access Point, which in this case would run a redaction API to remove PII from the reports.

Operational Efficiency: S3 Object Lambda handles data processing on the fly, without requiring the data to be permanently transformed or moved to another service (like Amazon Redshift).

Alternatives:

Option A: Loading the data into Amazon Redshift would require refactoring the analytics service and maintaining an additional data pipeline, increasing complexity.

Option C: Using AWS KMS for encryption protects data at rest and in transit, but it does not address PII redaction.

Option D: SNS is a messaging service and does not support direct data transformation.