Clarify requirements & constraints
- Scope: primary data, backups/snapshots, caches/CDNs, ephemeral stores, third‑party processors
- SLAs: retention vs legal‑hold durations, jurisdictional compliance, e‑discovery timelines, need for deletion proof
High‑level process
- Central Legal‑Hold Service: single source of truth storing holds, scope (IDs, types, tenants), start/end, custodians, and escalation. Exposes APIs consumed by systems and auditors.
- Policy Engine: translates holds into enforcement (prevent deletion, mark immutable, quiesce backups) and communicates to storage/KMS/CDN/third parties.
- Provenance & Audit Trail: tamper‑evident append‑only ledger (e.g., cloud KVS + cryptographic hashing or ledger service) recording hold creation, scope changes, deletion requests, and all erase actions.
Technical controls per surface
- Primary data: mark object metadata with hold flags; place objects into immutable containers (WORM/Retention). Deny delete via RBAC + policy engine.
- Backups/snapshots: snapshot lifecycle manager checks active holds before pruning; create protected snapshots tagged with hold IDs; store backups in immutable storage tier.
- Caches/CDNs/ephemeral: on hold apply bypass markers; ensure cache TTLs set to 0 or purge endpoints honor hold; record purge suppression in audit.
- Encryption key destruction: for guaranteed deletion, support crypto‑shredding by destroying KMS key version; log key destruction event and link to data key IDs and manifests.
- Third‑party processors: contractual SLOs + API hooks; require attestation, X‑509 signed deletion confirmations, and push manifests back to central ledger.
Proving deletion/preservation
- Preservation proof: export signed manifests listing object IDs, hashes, storage locations, timestamps, and hold IDs; store manifest in append‑only ledger. Provide immutable snapshots of storage metadata.
- Deletion proof: for physical deletion, provide deletion manifest with object IDs, timestamps, storage node IDs, and operation hashes; for crypto‑shred, provide signed KMS key destruction certificate plus mapping of keys -> object envelopes and previous object hashes.
- Audit evidence: ledger proofs (Merkle roots), access control logs, backup lifecycle records, network egress records to show no exfiltration, and third‑party signed attestations.
Scalability & reliability
- Event‑driven propagation (queue + retries) to enforce holds across regions.
- Periodic reconciliations and sampling-based proofing at scale.
- Playbooks for legal/unexpected failures (freeze, export, manual quarantine).
Trade‑offs
- Immutable retention vs storage cost; crypto‑shred faster but may not satisfy physical media requirements in some jurisdictions—keep dual strategy (logical & physical where needed).
Outcome: single authoritative hold system + immutable provenance ledger + enforced technical controls across all data surfaces, producing cryptographically signed manifests and KMS attestations auditors and legal teams can verify.
