# Functions

Functions are serverless Python and Node handlers with fast cold starts and scale-to-zero. You paste a handler and get a public URL - no repo, no Dockerfile, no server to manage. They're ideal for webhooks, small APIs, scheduled tasks, and MCP endpoints.

## Creating a function

1. Go to **Functions -> New Function**.
2. Pick a runtime (Python 3.10-3.13 or Node 18-24).
3. Paste your handler code, and dependencies if you need any.
4. Deploy. You get a URL like `fn-{name}.orkestr.run`.

```python
# Python - return JSON
def handler(event):
    name = event.get("query", {}).get("name", "world")
    return {"hello": name}
```

```javascript
// Node.js - echo the request back
exports.handler = async (event) => {
  return { method: event.method, path: event.path, query: event.query };
};
```

## The event object

Your handler receives an `event` describing the incoming request - method, path, query parameters, headers, and body. Return a value and orkestr serializes it as the response. Functions are plain request/response, so they fit anything that speaks HTTP.

## Dependencies

Declare dependencies alongside the handler (for example a requirements-style list for Python or packages for Node). They are installed when the function is built, so imports are available at runtime.

```bash
httpx==0.27.0
pydantic==2.9.0
```

## Function vs project

A function is a single handler with no repo or Dockerfile that scales to zero between requests and is sized by your plan. A [project](https://orkestr.eu/docs/features/projects) is a full application built from a repo and kept running. Reach for a function when you just need an endpoint; reach for a project when you have an app. For running a command inside an existing app, use a [job](https://orkestr.eu/docs/features/jobs).

## Cold starts and scale-to-zero

Functions scale to zero when idle and cold-start on the next request. Higher plans allocate more CPU and memory, so cold starts are faster. Because you only run during invocations, an idle function costs nothing in resources.

## Authentication

Functions are public by default. Switch a function to `api_key` mode and orkestr issues a key callers must send in the `X-Orkestr-API-Key` header. You can rotate the key at any time; the old key stops working immediately.

## Testing and metrics

- Use the built-in test console on the function page to send a request and see the status, body, headers, and duration.
- View request metrics per function over a selectable time window.
- Fetch recent logs from the function page.

## Resources and limits

- CPU and memory are plan-driven (faster cold starts on higher tiers), not user-configurable.
- Starter: 1 function. Pro: 10. Enterprise: custom.
- Idle functions scale to zero and cold-start on the next request.

> **Schedule a function**
>
> Use a [Cron](https://orkestr.eu/docs/features/crons) to call a function on a recurring schedule - nightly reports, cache warmers, polling integrations.

## FAQ

### Can a function reach a database?

Yes, over the network with credentials you provide as configuration. For work that needs your app's exact environment and code, a job is usually the better fit.

### What languages are supported?

Python 3.10-3.13 and Node 18-24.

### Can I use a function as an MCP endpoint?

Yes - functions are a common way to host small MCP servers and webhooks with a stable URL.

### How do I secure a function?

Switch it to api_key mode and send the issued key in the X-Orkestr-API-Key header; rotate the key whenever you need.