page:guides:fastapi:object client

Configure S3-compatible access for FastAPI

Summary

Configure S3-compatible access for a FastAPI app on Ample. Create a bucket with ample bucket create, pass its endpoint, region, bucket name and keys as encrypted environment variables, and use boto3 with Config(s3={'addressing_style': 'path'}). The app writes and reads objects through the S3-compatible endpoint; the bucket stays private.

Prerequisites

An S3 client in the app (boto3 with Config(s3={'addressing_style': 'path'})) reading S3_ENDPOINT, S3_REGION, S3_BUCKET, S3_ACCESS_KEY_ID and S3_SECRET_ACCESS_KEY
A bucket created with ample bucket create and its credentials from ample bucket credentials
An Ample account token with servers:write and buckets:read

Workflow Steps

Create the bucket
Create it once and keep the issued credentials out of the repository.
```
ample bucket create --name <bucket-name>
```
Configure the client with path-style addressing
Use boto3 with Config(s3={'addressing_style': 'path'}); virtual-host addressing is not verified.

Deploy with the credentials as encrypted env
Pass the five S3_* variables with --env; they are stored encrypted and reused on redeploys.

ample deploy . --name <app-name> --public --start "python3 run.py" --env S3_ENDPOINT=... --env S3_REGION=... --env S3_BUCKET=... --env S3_ACCESS_KEY_ID=... --env S3_SECRET_ACCESS_KEY=...

Test through the app
Expose a route (/storage) that writes then reads an object and reports s3=ok.
Verify
Fetch the live URL and run the success checks below. On failure read the build log, then the runtime log, fix the cause and deploy again; do not blind-retry.
```
ample logs <app-name> --kind build
```

Success Checks

object write and read succeed
- Type: http_get
- Path: /storage
- Expect: s3=ok

Limitations

Verified on the node-22 template at s-1vcpu-1gb; other templates and sizes are not verified by this recipe.
Region, compliance attestations and request-duration limits are unknown and not claimed.
Apps auto-pause when idle and wake on the next request; always-on is an operator setting, not a plan feature.

Cost Estimate

Monthly Amount: $5.00
Basis: size prices from pricing.toml at build revision 1ac5595375130d45290090e82ed0f554ccd45405-dirty
Note: Compute only. Buckets are allocation-priced per quota and capped by the plan; see ample usage.

Evidence Summary

kind: canary_run
summary: FastAPI app using boto3 (path-style addressing) with injected bucket credentials: put_object then get_object returned s3=ok. observedAt: 2026-09-20T01:13:26Z
kind: canary_run
summary: ample bucket create issued credentials; PutObject and GetObject succeeded through the public S3 endpoint. observedAt: 2026-09-20T01:13:26Z