# Host ai chat application with Fastify: Postgres-backed state

Deploy an ai chat application built with Fastify on Ample using the durable job state 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 Fastify: a jobs table with a state and attempts counter, processing inside a row-locked transaction, and a second run that is a no-op (job=done attempts=1 idempotent=true). Not separately tested: your job types, payload schema and retry policy; treat the ai chat application-specific behavior as your application code.

## Summary

- **Framework**: Fastify  
- **Workload**: AI chat application  
- **Release status**: published  
- **Support status**: verified  
- **Execution status**: ready  
- **Docs only**: false

## Prerequisites

- A Fastify project that builds and starts with the documented commands (npm install, npm run build --if-present, npm run start on the node-22 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

## Resource Requirements

- Compute
- Postgres

## Workflow Steps

1. **Build and start**: `npm install`, `npm run build --if-present`, `npm run start` on the node-22 template. The server must bind 0.0.0.0 on PORT.
2. **Implement the pattern on PostgreSQL**: The fixture's module implements durable job state: a jobs table with a state and attempts counter, processing inside a row-locked transaction, and a second run that is a no-op (job=done attempts=1 idempotent=true). 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/durable-job-state) from the example; then run your own checks. On failure read `ample logs --kind build` then `--kind runtime`.
   Command: `ample logs --kind build`

## Input Schema

```json
{
  "additionalProperties": false,
  "properties": {
    "env": {
      "description": "Encrypted environment variables (bucket credentials, secrets)",
      "items": {
        "pattern": "^[A-Z][A-Z0-9_]*=.*$",
        "type": "string"
      },
      "maxItems": 50,
      "type": "array"
    },
    "name": {
      "description": "App name",
      "maxLength": 63,
      "minLength": 1,
      "pattern": "^[a-z0-9-]+$",
      "type": "string"
    },
    "path": {
      "description": "Project directory or ample.toml service",
      "maxLength": 512,
      "minLength": 1,
      "type": "string"
    },
    "release_command": {
      "description": "Migration command run before activation",
      "maxLength": 512,
      "type": "string"
    }
  },
  "required": ["name", "path"],
  "type": "object"
}
```

## Examples

- **Fastify pattern fixture**: Multi-pattern Fastify app whose durable job state module was checked live; the module is under tests/deploy-canaries/_pattern-modules.

## Cost Estimate

- **Currency**: USD  
- **Monthly Amount**: $10.00  
  - **Components**:  
    - **App server**: s-1vcpu-1gb, quantity: 1.0, monthlyAmount: $5.00  
    - **Managed PostgreSQL database**: s-1vcpu-1gb, quantity: 1.0, monthlyAmount: $5.00

## Limitations

- Verified on the node-22 template at s-1vcpu-1gb with the example fixture; other sizes, templates and Fastify major versions are not verified.
- The ai chat application itself (your job types, payload schema and retry 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.