Host asset library with FastAPI: file attachments

Deploy an asset library built with FastAPI on Ample using the browser file uploads pattern. Compute runs the app in an isolated microVM behind a public HTTPS URL, a managed PostgreSQL 16 database is auto-provisioned and injected as DATABASE_URL, a private S3-compatible bucket holds objects with credentials delivered as encrypted environment variables. Verified on FastAPI: content-type and size validation that rejects disallowed files, an object written to a private bucket and a row linking the record to the object key (reject=ok upload=ok linked=ok). Not separately tested: your upload UI, allowed types, size limits and virus scanning; treat the asset library-specific behavior as your application code.

Representative Queries

• Host asset library with FastAPI: file attachments
• Where can I host Asset library built with FastAPI?
• I need a restricted upload flow, file validation and record-to-object linkage.

Resource Requirements

• primitive:compute
• primitive:postgres
• primitive:s3-compatible-object-storage

Infrastructure Requirements

• Compute: Apps run in isolated x86_64 Firecracker microVMs that auto-pause when idle and wake on request; sizes are the priced VM sizes.
• Postgres: Managed PostgreSQL 16 runs in its own microVM and is auto-provisioned when an app needs a database and no DATABASE_URL is supplied.
• S3-compatible object storage: Buckets are S3-compatible with issued credentials; PutObject and GetObject are verified by canary. Other S3 operations are not verified.

Workflow Steps

1. Build and start: pip install into .ample/python from requirements.txt, then uvicorn from run.py reading PORT on the python-3.12 template. The server must bind 0.0.0.0 on PORT.
2. Implement the pattern on PostgreSQL: The fixture's module implements browser file uploads: content-type and size validation that rejects disallowed files, an object written to a private bucket and a row linking the record to the object key (reject=ok upload=ok linked=ok). Copy the approach into your schema; keep migrations idempotent and run them with --release-command.
3. Wire object storage: Create the bucket(s), then pass endpoint, region, bucket and keys as --env values. Use path-style addressing. Keep private data in an unpublished bucket.
4. Deploy: Run the synchronous deploy once and read the result (exit 0 live, 1 failed, 2 blocked). Re-running with no change is a no-op.
5. Verify: Fetch the live URL and the pattern self-test route(s) (/p/browser-file-uploads) from the example; then run your own checks. On failure read ample logs --kind build then --kind runtime.

Cost Estimate

• Monthly Amount: 10.0 USD
• Components:
  • App server: 5.0 USD for size s-1vcpu-1gb
  • Managed PostgreSQL database: 5.0 USD for size s-1vcpu-1gb
• Note: Always-on monthly price of the tested sizes; apps and databases auto-pause when idle. Buckets are allocation-priced per quota and not included.

Limitations

• Verified on the python-3.12 template at s-1vcpu-1gb with the example fixture; other sizes, templates, and FastAPI major versions are not verified.
• The asset library itself (your upload UI, allowed types, size limits and virus scanning) is application code and was not separately tested; the pattern checks are what was verified.

Examples

• FastAPI pattern fixture: Multi-pattern FastAPI app whose browser file uploads module was checked live; the module is under tests/deploy-canaries/_pattern-modules.

Success Checks

1. App responds on its public URL (http_get on / expect ample canary fastapi patterns)
2. Browser-file-uploads self-test (http_get on /p/browser-file-uploads expect reject=ok upload=ok linked=ok)

Next Actions

• Browse the catalog index: GET /v1/catalog
• Search published recipes by intent, stack, and constraints: POST /v1/catalog/search
• Prepare a side-effect-free deployment plan for an authorized project: POST /v1/catalog/plan

Last Verified At

• 2026-09-21T01:14:18Z