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

# Upload a part

> Store one part of an in-flight upload. A part holds at most
5 GiB; every part except the last one named at completion must
be at least 5 MiB, which completion is where that floor is
checked.




## OpenAPI

````yaml /api-reference/specs/storage.yaml put /v1/buckets/{bucket}/multipart-uploads/{upload_id}/parts/{part_number}
openapi: 3.0.3
info:
  title: Basaltic Storage API
  version: 1.0.0
  description: |
    Block volumes with their snapshots and snapshot policies, plus bucket
    management for object storage. The S3 wire protocol itself is served
    separately at `objects.{region}.basaltic.cloud`.
  contact:
    name: Basaltic Support
    email: ping@basaltic.sh
  license:
    name: Proprietary
    url: https://basaltic.sh/terms
servers:
  - url: https://storage.{region}.basaltic.sh
    description: Regional API endpoint
    variables:
      region:
        default: sa-saopaulo-1
        description: Region code
security:
  - SignatureAuth: []
paths:
  /v1/buckets/{bucket}/multipart-uploads/{upload_id}/parts/{part_number}:
    parameters:
      - name: bucket
        in: path
        required: true
        schema:
          type: string
          example: my-app-assets
      - name: upload_id
        in: path
        required: true
        schema:
          type: string
          example: 2~tHc6Lc1fQy0Q
      - name: part_number
        in: path
        required: true
        schema:
          type: integer
          minimum: 1
          maximum: 10000
          example: 1
    put:
      tags:
        - Buckets
      summary: Upload a part
      description: |
        Store one part of an in-flight upload. A part holds at most
        5 GiB; every part except the last one named at completion must
        be at least 5 MiB, which completion is where that floor is
        checked.
      operationId: uploadPart
      requestBody:
        required: true
        content:
          application/octet-stream:
            schema:
              type: string
              format: binary
      responses:
        '200':
          description: Part stored.
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/UploadPartResponse'
        '400':
          description: Invalid part number, too many parts, or part too large.
        '401':
          $ref: '#/components/responses/Unauthorized'
        '403':
          description: Caller lacks the required IAM permission.
        '404':
          description: No such bucket or upload.
      security:
        - SignatureAuth: []
components:
  schemas:
    UploadPartResponse:
      type: object
      required:
        - part_number
        - etag
        - size
      properties:
        part_number:
          type: integer
          example: 1
        etag:
          type: string
          example: '"d41d8cd98f00b204e9800998ecf8427e"'
        size:
          type: integer
          format: int64
          example: 5242880
    Error:
      type: object
      required:
        - error
      properties:
        error:
          type: object
          required:
            - code
            - message
            - request_id
          properties:
            code:
              type: string
              description: Error code identifying the type of error
              example: INVALID_INPUT
            message:
              type: string
              description: Human-readable error message
              example: Invalid request parameters
            request_id:
              type: string
              format: uuid
              description: Request ID for debugging
              example: 550e8400-e29b-41d4-a716-446655440000
  responses:
    Unauthorized:
      description: Authentication required or token invalid
      content:
        application/json:
          schema:
            $ref: '#/components/schemas/Error'
          example:
            error:
              code: UNAUTHORIZED
              message: Authentication required
              request_id: 550e8400-e29b-41d4-a716-446655440000
  securitySchemes:
    SignatureAuth:
      type: apiKey
      in: header
      name: Authorization
      description: >
        Request signing with an access key issued to a service account. An

        HMAC-SHA256 over a canonical form of the request, close to AWS SigV4.

        The `basaltic` CLI signs for you.


        Send `Authorization`, `X-Date` (UTC, `YYYYMMDDTHHMMSSZ`) and `X-Nonce`

        (random per request); add `X-Content-Sha256` to bind a body, and

        `X-Amz-Security-Token` when using temporary credentials.


        ```

        Authorization: BASALTIC-HMAC-SHA256
        Credential=<access_key_id>/<date>/<region>/basaltic/basaltic_request,
        SignedHeaders=host;x-date;x-nonce, Signature=<hex>

        ```


        `<region>` is the region code you are calling, or `global` for the
        global

        services. A signature is valid for 5 minutes from `X-Date`, and mutating

        requests are replay-guarded on the nonce.


        **Full signing procedure, including a working implementation:**

        https://docs.basaltic.sh/authentication


        ## Rate limits

        There is no global request budget. A limit applies only where an

        operation documents a `429`, and that operation says what it counts.

        Those responses carry `X-RateLimit-Limit`, `X-RateLimit-Remaining`,

        `X-RateLimit-Reset` and, on a `429`, `Retry-After` — read them rather

        than hard-coding a number. Retrying before `Retry-After` is refused and

        extends the window. Everything else is bounded by quota, not by request

        rate.

````