## Host mobile backend with Express: streamed responses

Deploy a mobile backend built with Express on Ample using the streaming response service 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 Express: 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). Not separately tested: your event schema, reconnection strategy and any per-request duration ceiling beyond the 70 seconds measured; treat the mobile backend-specific behavior as your application code.

### Prerequisites
- A Express 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**: 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.

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

### 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 streaming response service: the observed behavior matches the aforementioned expectations. 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 routes and 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**: `GET /` expects output `ample canary express patterns`.
- **Streaming response service self-test**: `GET /p/streaming-response-service` expects a Server-Sent Events stream behavior as described.

### Limitations
- Verified on the node-22 template at s-1vcpu-1gb with the example fixture; other sizes, templates, and Express major versions are not verified.
- The mobile backend-specific behavior is not separately tested; the pattern checks are what was verified.
- Managed PostgreSQL 16 only; extensions, connection limits and backup or restore procedures are not verified.

### Cost Estimate
- **Currency**: USD
- **Monthly Amount**: 10.0
- **Components**:
  - **App server**: s-1vcpu-1gb, quantity: 1, monthly amount: 5.0
  - **Managed PostgreSQL database**: s-1vcpu-1gb, quantity: 1, monthly amount: 5.0
- **Note**: Always-on monthly price; apps and databases auto-pause when idle.

### Evidence Summary
- **Canary run**: Express pattern fixture deployed on Ample; checks passed for streaming-response-service and configuration-secrets.
  - **Observed At**: 2026-09-21T02:34:39Z
  - **Implementation Revision**: 1d28ae0-dirty (CLI 0.1.21)
- **Canary run**: Same Express app deployed with a --release-command migration.
  - **Observed At**: 2026-09-20T01:54:51Z

### Next Actions
- **Browse the catalog index**: [GET /v1/catalog](<url>)
- **Search published recipes by intent, stack, and constraints**: [POST /v1/catalog/search](<url>)
- **Prepare a side-effect-free deployment plan for an authorized project**: [POST /v1/catalog/plan](<url>)
- **Read the existing agent authentication setup**: [GET /mcp/setup](<url>)