# Host ai chat application with NestJS: streamed responses

## Summary

Deploy an AI chat application built with NestJS on Ample using the streaming response service pattern. Compute runs the app in an isolated microVM behind a public HTTPS URL, and a managed PostgreSQL 16 database is auto-provisioned and injected as DATABASE_URL. Verified on NestJS: a Server-Sent Events endpoint read incrementally through the public HTTPS gateway: five one-second chunks arrived spread over time with the first within seconds (not buffered), a 70-second stream of 36 chunks completed past common 60-second idle timeouts, and a client that disconnected after two chunks was observed and recorded by the server (disconnected=true).

## Infrastructure requirements

- Compute: verified (Apps run in isolated x86_64 Firecracker microVMs that auto-pause when idle and wake on request; sizes are the priced VM sizes.)
- Postgres: verified (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

## Exact tested configuration

- template: `node-22`
- runtime: `node`
- size: `s-1vcpu-1gb`
- install: `npm install`
- build: `npm run build --if-present`
- start: `npm run start`

## 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.** 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).

```
   ample deploy . --name <app-name> --public
   ```
4. **Verify.** Fetch the live URL and the pattern self-test route(s); then run your own checks.

```
   ample logs <deployment_id> --kind build
   ```

## Tested examples

- **NestJS pattern fixture**: Multi-pattern NestJS app whose streaming response service module was checked live; the module is under tests/deploy-canaries/_pattern-modules.

## Success checks

- App responds on its public URL (`/` on the live URL, expect ample canary NestJS patterns)
- Streaming-response-service self-test (`/p/streaming-response-service` on the live URL, expect an SSE stream: data: id=<uuid>, then chunk events one interval apart (read incrementally))

## 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 is application code and was not separately tested.

## Cost estimate

Estimated 10.00 USD per month.

## Verification evidence

- Canary_run on 2026-09-21T02:34:39Z at revision `1d28ae0-dirty (CLI 0.1.21)`: NestJS pattern fixture deployed on Ample (npm install, nest build (TypeScript) then node dist/main.js on the node-22 template); checks passed for streaming-response-service and configuration-secrets.

Last verified: 2026-09-21T02:34:39Z

## Execution binding

MCP tool `ample_deploy`, binding state `current`, required scopes: servers:write, databases:read.