Amazon EBS encryption is the right choice because it encrypts data at rest for EBS-backed storage by using AWS KMS and does so transparently. AWS documentation states that encrypted EBS volumes provide thesame IOPS performance as unencrypted volumes, with only a minimal effect on latency, which fits the requirement to avoid meaningful performance impact. Writing to S3 changes the storage architecture. A custom encryption algorithm would add development and operational complexity. Encrypting only the AMI root volume does not ensure the attached application data volumes are protected, and ephemeral disks are not the intended persistent storage here. Therefore, usingencrypted EBS volumesis the simplest and correct solution. (AWS Documentation)

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