# Host asset library with FastAPI: relational workflow state

## Summary
Deploy a asset library built with FastAPI on Ample using the transactional workflows 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. Verified on FastAPI: an optimistic version check and an event row written in the same transaction, a stale update rejected, and a history query over the application-owned events (history=2 conflict=rejected). Not separately tested: your domain records, validation rules and concurrency policy; treat the asset library-specific behavior as your application code.

## Representative Queries
- Host asset library with FastAPI: relational workflow state
- Where can I host Asset library built with FastAPI?
- I need a domain record schema, validation rules and concurrency behavior.

## Resource Requirements
- **Primitive Compute**
- **Primitive Postgres**

## Framework
FastAPI

## Workload
Asset library

## Release Status
published

## Support Status
verified

## Execution Status
ready

## Prerequisites
- A FastAPI project that builds and starts with the documented commands (pip install into .ample/python from requirements.txt, then uvicorn from run.py reading PORT on the python-3.12 template)
- A PostgreSQL driver reading DATABASE_URL at runtime (auto-provisioned when omitted, or supplied with --env)
- An Ample account token with servers:write, databases:read

## 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 transactional workflows: an optimistic version check and an event row written in the same transaction, a stale update rejected, and a history query over the application-owned events (history=2 conflict=rejected). Copy the approach into your schema; keep migrations idempotent and run them with --release-command.

3. **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.
   
   `ample deploy . --name  --public --start "python3 run.py"`

4. **Verify**  
Fetch the live URL and the pattern self-test route(s) (/p/transactional-workflows) from the example; then run your own checks. On failure read `ample logs  --kind build` then `--kind runtime`.
   
   `ample logs  --kind build`

## Examples
- **FastAPI pattern fixture**  
Multi-pattern FastAPI app whose transactional workflows module was checked live; the module is under tests/deploy-canaries/_pattern-modules.

## Success Checks
- app responds on its public URL  
  - `http_get` to path `/` should expect to see `ample canary fastapi patterns`
- transactional-workflows self-test  
  - `http_get` to path `/p/transactional-workflows` should expect `tx=ok history=2 conflict=rejected`

## 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 domain records, validation rules and concurrency policy) is application code and was not separately tested; the pattern checks are what was verified.

## Cost Estimate
- **Currency:** USD  
- **Monthly Amount:** $10.00  
- **Basis:** size prices from pricing.toml (loaded by the API) at build revision 1ac5595375130d45290090e82ed0f554ccd45405-dirty  
- **Components:**  
  - `app server`, size `s-1vcpu-1gb`, quantity `1`, monthly amount `$5.00`  
  - `managed PostgreSQL database`, size `s-1vcpu-1gb`, quantity `1`, monthly amount `$5.00`  
- **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.

## Last Verified At
2026-09-21T01:14:18Z

## Formats
- **HTML:** [link](/content/recipes/asset-library/fastapi/relational-workflow/index.html)  
- **Markdown:** [link](/content/recipes/asset-library/fastapi/relational-workflow.md)  
- **JSON:** [link](https://api.ample.computer/v1/catalog/recipes/page%3Arecipes%3Aasset-library%3Afastapi%3Arelational-workflow)

## Next Actions
- Browse the catalog index: `GET /v1/catalog`  
- Search published recipes by intent: `POST /v1/catalog/search`
- Prepare a deployment plan: `POST /v1/catalog/plan`
- Authenticate setup: `GET /mcp/setup`
- Browse Asset Library: `GET /v1/catalog/nodes/workload%3Aasset-library`  
- Browse FastAPI: `GET /v1/catalog/nodes/stack%3Aframework-fastapi`  
- Browse Transactional workflows: `GET /v1/catalog/nodes/pattern%3Atransactional-workflows`  
- Browse Deploy web app: `GET /v1/catalog/nodes/intent%3Adeploy-web-app`