# Limits (/tools/s3-gateway/limits)

| Limit                            | Value                                         | Amazon S3   | What happens past it                                        |
| -------------------------------- | --------------------------------------------- | ----------- | ----------------------------------------------------------- |
| Single `PutObject`               | 5 GiB                                         | 5 GiB       | `400 EntityTooLarge`. Use a multipart upload.               |
| Multipart part size              | 5 MiB to 5 GiB (the last part can be smaller) | Same        | `400 EntityTooSmall` or `400 EntityTooLarge`                |
| Parts per upload                 | 3,000                                         | 10,000      | `400 InvalidArgument` on the part that crosses the limit    |
| Largest object                   | About 14.6 TiB (3,000 × 5 GiB)                | 50 TiB      | —                                                           |
| Object key length                | 958 bytes                                     | 1,024 bytes | Keys from 959 to 1,024 bytes fail with `500 InternalError`  |
| Keys per `ListObjects` page      | 1,000                                         | 1,000       | `400 InvalidArgument` for `max-keys` above 1,000            |
| Keys per `DeleteObjects` request | 1,000                                         | 1,000       | `400 MalformedXML`                                          |
| Clock skew                       | Under 15 minutes                              | 15 minutes  | `401`                                                       |
| `Content-Length`                 | Required on uploads                           | Required    | `411 MissingContentLength`                                  |
| Presigned URL lifetime           | 1 second to 7 days                            | 7 days      | `400`: "X-Amz-Expires must be between 1 and 604800 seconds" |

On the [Free plan](/protocol/pricing#free-plan), an upload that would take you past your
10 GiB storage allowance is refused with `400 EntityTooLarge` before any data is sent. The
[console](https://console.shelby.xyz) shows your usage.

## Choosing a part size

Use parts of at least 10 MiB. Each part counts as at least 10 MiB of storage, so smaller parts
make a file count as more than it holds. See
[The 10 MiB minimum](/protocol/pricing#the-10-mib-minimum). The AWS CLI and boto3 default to
8 MiB parts, and the AWS SDK for JavaScript and rclone to 5 MiB, so each
[quickstart](/tools/s3-gateway/quickstarts/aws-cli) sets a larger part size.

Because of the 3,000-part limit, your part size also sets your largest file:

| Part size | Largest file  |
| --------- | ------------- |
| 10 MiB    | About 29 GiB  |
| 64 MiB    | About 187 GiB |
| 512 MiB   | About 1.5 TiB |

rclone and DuckDB raise the part size for you when told the limit: `max_upload_parts=3000` in
the [rclone quickstart](/tools/s3-gateway/quickstarts/rclone), and
`s3_uploader_max_parts_per_file = 3000` in the
[DuckDB quickstart](/tools/s3-gateway/quickstarts/duckdb).

## Concurrent downloads

Your organization can have a limited number of downloads in flight at once, shared by all of
its buckets and access keys. Every GET counts as one, including each range request and each
GET through a [presigned URL](/tools/s3-gateway/presigned-urls). HEAD requests don't count.

Past the limit, Shelby returns `503 SlowDown` with `Retry-After: 1`. AWS SDKs retry it for you.
If it keeps happening, lower your client's parallelism. A web page that loads many presigned
images or videos at once can hit it too, because a video player makes a series of range
requests as it plays.

## What isn't limited

Objects stay until you delete them. Shelby has no lifecycle rules or automatic expiry.