Create separate AWS Glue ETL jobs per hospital and attach a security configuration that uses that hospital's AWS KMS key for SSE-KMS during job runs and for objects written to Amazon S3 is correct because it lets you enforce per hospital encryption boundaries while using a serverless service that minimizes day to day operations.

This approach uses Glue security configurations to bind each job to a hospital specific AWS KMS customer managed key so data at rest in S3 and temporary job artifacts are encrypted with the required key and access is auditable. SSE-KMS ensures objects are encrypted with customer managed keys rather than S3 managed keys and you can apply key policies and monitor key usage through CloudTrail which helps satisfy compliance.

Use AWS Glue to run a single multi-tenant ETL job for all hospitals, tag records by hospital, and select a hospital's AWS KMS key dynamically to write results to Amazon S3 with SSE-KMS is less desirable because a single multi tenant job requires complex branching and dynamic key selection and that increases the risk of misrouting data or misconfiguring encryption compared with per hospital jobs bound to specific keys.

Build containerized ETL with AWS Batch on Fargate, encrypt task storage with KMS and write outputs to Amazon S3 using SSE-S3 adds significant operational overhead since you must build maintain and scale containers and orchestration. In addition SSE-S3 does not meet the requirement for customer managed per hospital keys because it uses S3 managed encryption keys.

Operate one shared Amazon EMR cluster for all hospitals, secure traffic with TLS, and store outputs in Amazon S3 using SSE-S3 fails the per hospital key requirement because TLS only protects data in transit and SSE-S3 uses S3 managed keys so you cannot enforce separate customer managed keys for each hospital.

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