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Object storage on Upsun adds an S3-compatible bucket to your application. You enable it by setting an object-storage size on the app’s resources. Upsun provisions the bucket and connects it to your app. Object storage is integrated with the rest of the platform. When you back up an environment, the bucket’s contents are included in the backup, and when you branch an environment, the bucket is cloned along with the environment’s other data. You manage it together with the rest of your project rather than as a separate service.
Object storage is currently a prerelease feature. To enable it on your project, open this prepopulated Support ticket and add your project ID before submitting.To get your project ID, run upsun projects and copy the corresponding ID.

When to use object storage

Use object storage when your app needs to store large or growing volumes of unstructured data (uploads, media, backups, generated artifacts) and you want to reach it through the S3 API. For small amounts of file data that a single instance reads and writes through the filesystem, a persistent mount is usually a better fit.

Enable object storage

Set an object-storage size on an app. The size is in MB, in the app:size format. Run upsun resources:set with the --object-storage option:
Terminal
For example, to give the myapp app 512 GB (524288 MB) of object storage:
Terminal
To view the current allocation, run upsun resources:get. When an app has object storage, the output includes an Object storage (MB) column.

Sizing rules

Object storage is allocated in fixed steps, within a minimum and a maximum. The size you request must be a multiple of the step and fall within these bounds:

Connect from your app

Enabling object storage adds a relationship named object-storage to your app. This relationship name is reserved. If your configuration already declares a relationship called object-storage, the deployment fails and you must rename the relationship to proceed. At runtime, the relationship is exposed through the PLATFORM_RELATIONSHIPS environment variable. The object-storage entry provides the connection details for an S3-compatible endpoint: The endpoint URL is http://<HOST>:<PORT>. The endpoint is reachable over your project’s internal network only and isn’t exposed publicly. A single bucket is created per app, named after the app. So an app named myapp reaches its bucket at http://<HOST>:<PORT>/myapp/<KEY>. When configuring your S3 client, note two requirements:
  • Use path-style addressing. The bucket name goes in the URL path (http://<HOST>:<PORT>/myapp/object.txt), not the hostname. Disable virtual-hosted-style addressing.
  • No credentials are required. The endpoint doesn’t use access keys. Configure your client with empty credentials and any placeholder region.

Example (Python, boto3)

Share a bucket across containers

Other containers can use an app’s bucket through a relationship:
  • A worker that doesn’t declare its own relationships block inherits the parent app’s relationships, including object-storage, with no extra configuration.
  • A worker with its own relationships block, another application, or a task can reach an application’s bucket by targeting that app’s object-storage endpoint:
.upsun/config.yaml
The relationship name on the left (bucket here) is yours to choose. Targeting an app that doesn’t have object storage configured fails the deployment.

Resize and remove

To resize, pass a new value that is a valid multiple of the step:
Terminal
Set the size to 0 to remove object storage from the app:
Terminal
Setting the size to 0, or removing the app, deletes the bucket and all of its contents on the next deployment. There’s no soft-delete or retention period. Back up any data you need before removing.
When you branch an environment and clone its data, the object-storage size is inherited along with the data, so the new environment keeps its bucket.

Limitations

  • Each app gets a single bucket, named after the app. Multiple buckets per app aren’t supported.
  • A bucket belongs to one app. Other containers can share it through a relationship, but buckets can’t be reassigned between apps.
  • The endpoint is internal to the project and isn’t exposed publicly.
  • The following S3 features aren’t implemented: bucket versioning, object locking, server-side encryption (SSE), access control lists (ACLs), bucket policies, and lifecycle policies. Requests for them return a “not implemented” error.
  • Concurrent writes to the same object are last-write-wins with no object locking.

Inspect the bucket from an SSH session

You can explore your bucket directly from a running container using the AWS CLI.

Run S3 commands

The endpoint requires no real credentials — set AWS_ACCESS_KEY_ID, AWS_SECRET_ACCESS_KEY, and AWS_DEFAULT_REGION to any arbitrary value. Use http://<HOST>:<PORT> as the endpoint URL, as described in Connect from your app.
Terminal
Other standard S3 commands work the same way:
Last modified on June 9, 2026