palaniappan p3 min
Amazon S3 SSE-C Default Disable (April 2026): Migration Playbook
After the April 2026 S3 default that blocks SSE-C on new buckets (and on existing buckets in accounts with zero SSE-C objects), a SaaS media platform (~2.4 PB, 418 buckets) found 11 legacy upload paths still sending customer-key headers — all failing 403 until migrated to SSE-KMS.