### Host event registration with FastAPI: relational workflow state

Deploy an event registration 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 event registration-specific behavior as your application code.

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

#### Resource Requirements
- primitive:compute
- primitive:postgres

#### 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. (Status: verified)
- **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. (Status: verified)

#### Prerequisites
1. 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).
2. A PostgreSQL driver reading DATABASE_URL at runtime (auto-provisioned when omitted, or supplied with --env).
3. 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.  
   Command: `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`.  
   Command: `ample logs  --kind build`

#### 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 event registration 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:** 10.0  
- **Basis:** Size prices from pricing.toml (loaded by the API) at build revision 1ac5595375130d45290090e82ed0f554ccd45405-dirty  
   - **Components:**
      - app server: s-1vcpu-1gb, quantity: 1.0, monthlyAmount: 5.0  
      - managed PostgreSQL database: s-1vcpu-1gb, quantity: 1.0, monthlyAmount: 5.0

### Evidence Summary
1. **Canary Run:** FastAPI pattern fixture deployed on Ample with checks passed for transactional-workflows and configuration-secrets.
   - **Observed At:** 2026-09-21T01:14:18Z  
   - **Implementation Revision:** 50dbac567d2c5cc8e55e6c748a646be0025d9cfb-dirty (CLI 0.1.21)
   - **Expires At:** 2027-03-20T01:14:18Z

2. **Canary Run:** The same FastAPI app deployed with a --release-command migration; the marker it created was readable after activation.
   - **Observed At:** 2026-09-20T01:54:51Z  
   - **Implementation Revision:** 199ff1dfd52683832ae75d3f98b53a7a4bff7f96-dirty (CLI e3181f5)  
   - **Expires At:** 2027-03-19T01:54:51Z

#### Next Actions
- **Browse the catalog index**  
   - Action ID: `browse-catalog`
   - Method: GET
   - Relative Path: `/v1/catalog`

- **Search published recipes by intent, stack and constraints**  
   - Action ID: `search-recipes`
   - Method: POST
   - Relative Path: `/v1/catalog/search`
   - Parameters: {"body":{"limit":5,"query":"Host event registration with FastAPI: relational workflow state"}}

- **Prepare a side-effect-free deployment plan for an authorized project**  
   - Action ID: `plan:page:recipes:event-registration:fastapi:relational-workflow`
   - Method: POST
   - Relative Path: `/v1/catalog/plan`