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

# Auto-scaling

> Scale a fleet by changing the desired instance count

Use a [spot deployment](/preview/spot-deployments) when you want SF Compute to maintain a target
number of instances and buy the compute to run them automatically. To scale, update the
deployment's target instance count. The deployment buys compute to cover new instances and offers
unneeded compute for sale when you scale down.

This pattern is useful for inference workers, batch workers, CI runners, or any other fleet where
the desired instance count changes over time.

## Prerequisites

* SF Compute CLI installed and authenticated (`sf login`)
* Credits on your account (`sf billing balance`)
* A sense of which hardware you want (`sf instance-skus list`)

## Create a pool

```bash theme={null}
sf pools create --name workers
```

## Create an instance template

Define the image and startup script for the instances in the fleet.

```bash startup.sh theme={null}
#!/bin/bash

mkdir -p /root/.ssh
cat >>/root/.ssh/authorized_keys <<"EOF"
ssh-ed25519 AAAA... you@example.com
EOF

# Start your worker process here
```

```bash theme={null}
sf instance-templates create \
  --name worker \
  --image ubuntu-22.04.5-cuda-12.7 \
  --cloud-init ./startup.sh
```

See [Instance templates](/preview/instance-templates) for details on cloud-init and image
configuration.

## Create a spot deployment

Pass `--instance-sku <id>` to pin the fleet to specific hardware; see
[instance SKUs](/preview/instance-skus) for the catalog.

```bash theme={null}
sf deployments create \
  --type spot \
  --name workers \
  --pool workers \
  --instance-template worker \
  --instance-sku isku_4UpxzQw7A8N \
  --target-instance-count 4 \
  --max-rate 20.00 \
  --min-runtime 2h
```

The deployment places buy orders for 4 instances. As orders fill, capacity lands on the pool and
instances move to `running`. `--max-rate` caps what the deployment pays, in dollars per node-hour.
`--min-runtime` sets the minimum continuous capacity window purchased before launching each
instance.

## Scale up

```bash theme={null}
sf deployments set workers --target-instance-count 8
```

4 new instances are queued. The deployment buys compute to cover them. Availability depends on
matching sell orders within your maximum rate.

## Scale down

```bash theme={null}
sf deployments set workers --target-instance-count 2
```

Excess instances stop and their remaining secured capacity is offered for sale. When a pool's
allocation drops below the number of running nodes, the newest nodes are terminated first. To
protect specific nodes from sale, transfer their allocation to a separate pool; see
[Protect nodes from termination](/preview/pools#protect-nodes-from-termination).

## Handling interruptions

<Warning>
  Spot compute is not guaranteed. Instances may shut down if the market price exceeds your maximum
  rate or other buyers place reservations that consume the capacity. Design workloads to handle
  instances being replaced.
</Warning>

* **Stateless workers.** Download model weights on boot. Local disk does not persist between
  instances.
* **Health check your load balancer.** Route traffic only to instances that are ready.
* **Longer `--min-runtime`.** A higher value (e.g., `6h`) buys a longer guaranteed window per
  instance but commits more spend per purchase.

## Monitoring

```bash theme={null}
sf deployments get workers   # Deployment status, target, and reconciliation
sf instances list            # Individual instance status
```

Spot-generated orders also appear in the pool's order history.

## Next steps

* Adjust `--max-rate` to control spend
* Buy a reserved block of compute on a separate pool with a standard
  [deployment](/preview/deployments) when part of the fleet must not be interrupted:
  ```bash theme={null}
  sf orders create --pool workers-reserved --side buy --nodes 4 --instance-sku isku_4UpxzQw7A8N --start "in 5h" --duration 24h --max-rate 20.00
  ```