Host form collection with FastAPI: relational workflow state

Deploy a form collection 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 form collection-specific behavior as your application code.

Representative Queries

• Host form collection with FastAPI: relational workflow state
• Where can I host Form collection built with FastAPI?
• I need a domain record schema, validation rules and concurrency behavior.

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

Tested Configuration

• Template: python-3.12
• Runtime: python
• Size: s-1vcpu-1gb
• Install: python3 -m pip install --target .ample/python -r requirements.txt
• Start: PYTHONPATH=.ample/python:${PYTHONPATH:-} python3 run.py

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

Success Checks

• App responds on its public URL

  • Kind: http_get
  • Path: /
  • Expect: ample canary fastapi patterns

• Transactional-workflows self-test

  • Kind: http_get
  • Path: /p/transactional-workflows
  • Expect: tx=ok history=2 conflict=rejected

Cost Estimate

• Currency: USD
• Monthly Amount: 10.0
• Note: Always-on monthly price of the tested sizes; apps and databases auto-pause when idle.
• Components:
  • App server: s-1vcpu-1gb, quantity: 1.0, monthly amount: 5.0
  • Managed PostgreSQL database: s-1vcpu-1gb, quantity: 1.0, monthly amount: 5.0

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 form collection itself (your domain records, validation rules and concurrency policy) is application code and was not separately tested.
• 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.

Examples

• FastAPI pattern fixture
  Multi-pattern FastAPI app whose transactional workflows module was checked live; the module is under tests/deploy-canaries/_pattern-modules.
  Source Reference: tests/deploy-canaries/fastapi-patterns

Next Actions

• Browse the catalog index
  Method: GET
  Relative Path: /v1/catalog
• Search published recipes by intent, stack and constraints
  Method: POST
  Relative Path: /v1/catalog/search
  Body: {"limit":5,"query":"Host form collection with FastAPI: relational workflow state"}
• Prepare a side-effect-free deployment plan for an authorized project
  Method: POST
  Relative Path: /v1/catalog/plan
  Body: {"inputs":{},"projectId":"","recipeId":"page:recipes:form-collection:fastapi:relational-workflow","recipeRevision":"r1"}
• Read the existing agent authentication setup
  Method: GET
  Relative Path: /mcp/setup