Amazon S3 Storage Lens with advanced activity metrics is the most operationally efficient answer because AWS documentation explicitly says you can use S3 Storage Lens advanced metrics to identify “cold” buckets, meaning buckets whose objects are no longer accessed or are accessed only rarely. That is exactly the requirement in the question. This avoids building a custom analytics workflow on top of CloudTrail or CloudWatch metrics. The standard S3 console does not provide the same purpose-built fleet-level analysis for cold-bucket identification. Athena and CloudTrail can be used for access analysis, but they require more setup, data handling, and query maintenance. S3 Storage Lens is the native managed feature for this storage-optimization scenario. (AWS Documentation)

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