# Host form collection with Phoenix: relational workflow state

Deploy a form collection built with Phoenix 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 Phoenix: 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 Phoenix: relational workflow state
- Where can I host Form collection built with Phoenix?
- 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.
- **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.

## Workflow Steps
1. **Build and start**  
   `mix deps.get, MIX_ENV=prod mix compile and mix release in the builder, then the release bin script with PHX_SERVER=true on the elixir-1.18 template; PORT, DATABASE_URL and SECRET_KEY_BASE read in config/runtime.exs.` 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`
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 phoenix patterns
- _transactional-workflows self-test_  
   **Kind**: http_get  
   **Path**: /p/transactional-workflows  
   **Expect**: tx=ok history=2 conflict=rejected

## Limitations
- Verified on the elixir-1.18 template at s-1vcpu-1gb with the example fixture; other sizes, templates and Phoenix 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; the pattern checks are what was verified.
- 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.
- Managed PostgreSQL 16 only; extensions, connection limits and backup or restore procedures are not verified; apps and their databases are placed together.

## 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_: size s-1vcpu-1gb, quantity 1.0, monthly amount 5.0
  - _managed PostgreSQL database_: size s-1vcpu-1gb, quantity 1.0, monthly amount 5.0
- **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.

## Evidence Summary
- **Kind**: canary_run  
  **Summary**: Phoenix pattern fixture deployed on Ample; checks passed for transactional-workflows and configuration-secrets. Pattern proof: 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.
  **Observed At**: 2026-09-20T23:45:31Z

## Formats
- **HTML**: [Link](/content/recipes/form-collection/phoenix/relational-workflow/index.html)
- **Markdown**: [Link](/content/recipes/form-collection/phoenix/relational-workflow.md)
- **JSON**: [Link](https://api.ample.computer/v1/catalog/recipes/page%3Arecipes%3Aform-collection%3Aphoenix%3Arelational-workflow)