page:recipes:event registration:fastapi:relational workflow

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

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  • Action ID: search-recipes
  • Method: POST
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  • Parameters: {"body":{"limit":5,"query":"Host event registration with FastAPI: relational workflow state"}}

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  • Action ID: plan:page:recipes:event-registration:fastapi:relational-workflow
  • Method: POST
  • Relative Path: /v1/catalog/plan