## Host ai chat application with Express: streamed responses

### Summary
Deploy an AI chat application built with Express 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 Express: a Server-Sent Events endpoint has 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).

### Representative Queries
- Host ai chat application with Express: streamed responses
- Where can I host AI chat application built with Express?
- I need a tested end-to-end streaming transport, timeout behavior, and client disconnect handling.

### Resource Requirements
- **Primitive Requirements**: `compute`, `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.

### Prerequisites
- An 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`

### 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 a streaming response service via a Server-Sent Events endpoint.
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.
4. **Verify**: Fetch the live URL and the pattern self-test route(s) from the example; then run your own checks.

### Cost Estimate
- **Currency**: USD
- **Monthly Amount**: 10.0
- **Components**:
  - App server (size: s-1vcpu-1gb): $5.00
  - Managed PostgreSQL database (size: s-1vcpu-1gb): $5.00

### Limitations
- Verified on the node-22 template at s-1vcpu-1gb; other sizes and versions are not verified.
- The behavior specific to the AI chat application itself is application code and not separately tested.
- Other parameters such as region availability and compliance attestations are unknown.

### Success Checks
- App responds on its public URL.
- Streaming-response-service self-test: Verify an SSE stream and that `/status` reports expected values.

### Evidence Summary
- **Canary Run**: The Express pattern fixture was deployed successfully on Ample with checks confirming streaming response service functionality.
- Observed behaviors include expected chunk deliveries and connection handling during disconnection events.

### Next Actions
- **Browse the catalog index**
- **Search published recipes by intent, stack, and constraints**
- **Prepare a side-effect-free deployment plan** 
- **Read the existing agent authentication setup**\
- **Browse AI chat application** 
- **Browse Express** 
- **Browse Streaming response service** 
- **Browse Deploy AI app**