Bkend Storage

---
name: bkend-storage
description: |
  bkend.ai file storage expert skill.
  Covers single/multiple/multipart file upload via Presigned URL,
  file download (CDN vs Presigned), 4 visibility levels (public/private/protected/shared),
  bucket management, and file metadata.

  Triggers: file upload, download, presigned, bucket, storage, CDN, image,
  파일 업로드, 다운로드, 버킷, 스토리지, 이미지,
  ファイルアップロード, ダウンロード, バケット, ストレージ,
  文件上传, 下载, 存储桶, 存储,
  carga de archivos, descarga, almacenamiento, cubo,
  telechargement, televersement, stockage, seau,
  Datei-Upload, Download, Speicher, Bucket,
  caricamento file, scaricamento, archiviazione, bucket

  Do NOT use for: database operations (use bkend-data), authentication (use bkend-auth).
user-invocable: false
agent: bkit:bkend-expert
allowed-tools:
  - Read
  - Write
  - Edit
  - Glob
  - Grep
  - Bash
  - mcp__bkend__*
imports:
  - ${PLUGIN_ROOT}/templates/shared/bkend-patterns.md
---

# bkend.ai Storage Guide

## Upload Methods

| Method | Use Case | Process |
|--------|----------|---------|
| Single | Normal files | Presigned URL -> PUT upload -> Register metadata |
| Multiple | Multiple files | Repeat single upload |
| Multipart | Large files | Initialize -> Part URLs -> Complete |

## Presigned URL

- Validity: 15 minutes
- PUT method with file binary
- Content-Type header required

## File Visibility (4 levels)

| Level | Access | URL Type |
|-------|--------|----------|
| public | Anyone | CDN URL (no expiry) |
| private | Owner only | Presigned URL (1 hour) |
| protected | Authenticated users | Presigned URL (1 hour) |
| shared | Specified targets | Presigned URL (1 hour) |

## Size Limits

| Category | Max Size |
|----------|----------|
| Images | 10 MB |
| Videos | 100 MB |
| Documents | 20 MB |

## Storage Categories

images, documents, media, attachments

## REST Storage API

| Method | Endpoint | Description |
|--------|----------|-------------|
| POST | /v1/files/presigned-url | Generate presigned URL |
| POST | /v1/files | Register metadata (complete upload) |
| GET | /v1/files | File list |
| GET | /v1/files/{id} | File detail |
| PATCH | /v1/files/{id} | Update metadata |
| DELETE | /v1/files/{id} | Delete file |
| GET | /v1/files/{id}/download-url | Generate download URL |

## MCP Storage Tool

| Tool | Purpose |
|------|---------|
| 7_code_examples_data | CRUD + file upload code examples |

## Upload Flow (Single File)

```
1. POST /v1/files/presigned-url -> { url, fileId }
2. PUT {url} with file binary + Content-Type header
3. POST /v1/files with { fileId, filename, contentType, size, visibility }
```

## Multipart Upload Flow (Large File)

```
1. POST /v1/files/multipart/init -> { uploadId }
2. POST /v1/files/multipart/urls -> [{ partNumber, url }]
3. PUT each part URL with file chunk
4. POST /v1/files/multipart/complete -> { file }
```