Add a per-backend rotation-driver matrix to docs/operations/kms-backend-security.md: who performs the rotation on each backend (RustFS for Vault KV2, Vault's Transit engine for Transit, AWS RotateKeyOnDemand for AWS, nobody for Local/Static), how periodic rotation must be scheduled on each (external scheduler for KV2 by design, Vault auto_rotate_period for Transit, AWS-native automatic rotation for AWS since RotateKeyOnDemand carries a lifetime quota), the NIST SP 800-38D 2^32 random-nonce AES-GCM wrap ceiling that Local/Static can never reset, and a pre-rotation checklist referencing the existing upgrade-ordering hard constraint.
Add the KmsKeyRotationOverdue Prometheus rule on rustfs_kms_oldest_key_rotation_age_seconds (400-day conservative default, warning severity, no traffic guard because it is direct gauge state) and its runbook response procedure in docs/operations/kms-observability-runbook.md, following the existing per-alert format.
Sharpen the runbook's rotation-timestamp paragraph with verified per-backend behavior: only Vault KV2 persists rotated_at (stamped in the same check-and-set write that commits the rotation), while Transit and AWS key listings always report it absent, so on those backends the gauge measures key age and does not reset on rotation. Update Threshold calibration and Coverage gaps for the new rule.
Validated with promtool check rules (7 rules, SUCCESS) and scripts/check_doc_paths.sh.
Part of rustfs/backlog#1636 (PR-4).
Add a Grafana dashboard for the four KMS backend operation metrics
emitted at the policy choke point, Prometheus alert rules with
conservative default thresholds (pending staging baseline calibration),
and an operations runbook documenting the metric contract and the
response procedure for each alert. Register the new alert rules file in
the observability READMEs.
Refs rustfs/backlog#1584 (part of rustfs/backlog#1562)
Zhengchao An