> ## Documentation Index
> Fetch the complete documentation index at: https://doc.blueapi.ir/llms.txt
> Use this file to discover all available pages before exploring further.

# ArtifactStore for Content-Addressed Model Storage

> Specification for the ArtifactStore in EMEP, covering content-addressed storage, tiering, garbage collection, and digital signatures.

The ArtifactStore is the blob storage layer for EMEP. It stores model weights, experiment artifacts, evaluation outputs, and provenance records. Content addressing guarantees integrity and deduplication. This page specifies the storage model, tiering policy, and garbage collection rules.

## Content-Addressed Storage

All artifacts are stored by their SHA-256 hash. The store API is:

```text theme={null}
ArtifactStore.put(data) -> hash
ArtifactStore.get(hash) -> data
ArtifactStore.exists(hash) -> bool
ArtifactStore.verify(hash) -> bool
```

Content addressing provides:

* Integrity verification: the hash proves the data matches the record
* Deduplication: identical artifacts store once regardless of origin
* Immutability: artifacts cannot be modified without changing their hash
* Referential stability: hashes are permanent identifiers

## Artifact Types

| Type               | Description                 | Typical Size   |
| ------------------ | --------------------------- | -------------- |
| model\_weights     | Serialized model parameters | 1-100 GB       |
| experiment\_record | JSON experiment metadata    | 1-100 KB       |
| evaluation\_output | Raw benchmark results       | 10 MB - 1 GB   |
| provenance\_chain  | Signed provenance records   | 10-50 KB       |
| genome             | JSON genome specification   | 1-10 KB        |
| event\_stream      | ExperimentTracker logs      | 100 KB - 10 MB |

## Storage Tiers

| Tier    | Latency | Cost     | Contents                                       |
| ------- | ------- | -------- | ---------------------------------------------- |
| Hot     | \< 10ms | High     | Active experiment artifacts, recent models     |
| Warm    | \< 1s   | Medium   | Completed experiment outputs, validated models |
| Cold    | \< 1min | Low      | Archived experiments, deprecated models        |
| Glacier | Hours   | Very Low | Long-term audit retention                      |

Tiering is automatic based on access patterns and artifact age. Active experiment artifacts stay in hot storage. Artifacts from COMPLETED experiments move to warm after 7 days. ARCHIVED experiments move to cold after 30 days. Audit-mandated artifacts move to glacier after 90 days.

## Garbage Collection

Artifacts are eligible for garbage collection when:

* No ModelRegistry record references them
* No ExperimentTracker record references them
* They are not part of a signed provenance chain
* Retention policy allows deletion

The garbage collector runs weekly. It scans for unreferenced artifacts and moves them to a quarantine zone for 30 days before permanent deletion. Quarantined artifacts can be restored by hash.

## Digital Signatures

Critical artifacts (model weights, provenance chains, release packages) are signed at upload time. Signatures are stored alongside the artifact and verified on retrieval.

```text theme={null}
signature = sign(private_key, hash)
verify(public_key, hash, signature) -> bool
```

See [Artifact Signing](/security/artifact-signing) for key management and verification protocols.

## API Operations

```text theme={null}
ArtifactStore.put(data, artifact_type, metadata) -> hash
ArtifactStore.get(hash, tier_preference) -> data
ArtifactStore.get_metadata(hash) -> ArtifactMetadata
ArtifactStore.delete(hash) -> bool  # soft delete to quarantine
ArtifactStore.restore(hash) -> bool  # from quarantine
ArtifactStore.get_referencing_records(hash) -> List[RecordRef]
```

## Integration

| Component         | Stored Artifacts                   |
| ----------------- | ---------------------------------- |
| ModelLoader       | Retrieves model weights by hash    |
| ExperimentTracker | Stores event streams and records   |
| EvaluationEngine  | Stores raw evaluation outputs      |
| ModelRegistry     | References weight archives by hash |
| Provenance system | Stores signed provenance chains    |

<Warning>
  Garbage collection does not delete artifacts referenced by active experiments, registered models, or signed provenance chains. An artifact with any live reference is retained regardless of age.
</Warning>

<Info>
  Content addressing means that uploading the same artifact twice returns the same hash. The ArtifactStore detects duplicates and stores only one copy. This saves storage when multiple experiments use the same parent model.
</Info>