> ## Documentation Index
> Fetch the complete documentation index at: https://docs.trycassian.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Instances

> GPU containers for your workloads.

## What is an instance?

A GPU container running your code. Comes with GPU, CPU, RAM, and persistent storage at `/workspace`.

## Lifecycle

```
cassian up   -> running
cassian down -> stopped (workspace saved)
```

## Resources

CPU and RAM are assigned automatically based on your GPU. No configuration needed.

## Idle auto-stop

Instances with no GPU or CPU activity for **30 minutes** are automatically stopped. Your workspace is saved before shutdown, so nothing is lost.

This means you will not get charged for forgetting to run `cassian down`.

## Switching GPU types

Run `cassian switch` to pick a different GPU. Your workspace volumes are cloud-backed so they attach to any node. You do not need to re-download your data.