## Host AI Chat Application with NestJS: Postgres-backed State

### Summary
Deploy an AI chat application built with NestJS 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 NestJS: 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.

### Representative Queries
- Host AI chat application with NestJS: Postgres-backed state
- Where can I host AI chat application built with NestJS?
- I need a durable state schema and retry/recovery semantics implemented by application code.

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

### Infrastructure Requirements
1. **Compute**: Apps run in isolated x86_64 Firecracker microVMs that auto-pause when idle and wake on request; sizes are the priced VM sizes.
2. **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.

### Prerequisites
- A NestJS project that builds and starts with the documented commands (npm install, nest build (TypeScript) then node dist/main.js 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

### Tested Configuration
- **Template**: node-22
- **Runtime**: node
- **Size**: s-1vcpu-1gb
- **Install**: npm install
- **Build**: npm run build --if-present
- **Start**: npm run start

### 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"
}
```

### Workflow Steps
1. **Build and Start**: npm install, nest build (TypeScript) then node dist/main.js 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`.

### Success Checks
- **App responds on its public URL**: Kind: http_get, Path: /, Expect: ample canary nestjs patterns
- **Durable-job-state self-test**: Kind: http_get, Path: /p/durable-job-state, Expect: job=done attempts=1 idempotent=true

### Limitations
- Verified on the node-22 template at s-1vcpu-1gb with the example fixture; other sizes, templates and NestJS 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.

### Cost Estimate
- **Currency**: USD
- **Monthly Amount**: 10.0
- **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**: NestJS pattern fixture deployed on Ample (npm install, nest build (TypeScript) then node dist/main.js on the node-22 template); checks passed for durable-job-state and configuration-secrets. Pattern proof: 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).
- **Observed At**: 2026-09-21T02:34:39Z
- **Implementation Revision**: 1d28ae0-dirty (CLI 0.1.21)
- **Expires At**: 2027-03-20T02:34:39Z

### Formats
- **HTML**: [Link](/content/recipes/ai-chat-application/nestjs/persistent-state/index.html)
- **Markdown**: [Link](/content/recipes/ai-chat-application/nestjs/persistent-state.md)
- **JSON**: [Link](https://api.ample.computer/v1/catalog/recipes/page%3Arecipes%3Aai-chat-application%3Anestjs%3Apersistent-state)