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# System prepended metadata

title: Scale Out & In

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# Scale Out & In
> - **Objective:** Scale out & in of a TiDB Cluster
> - **Prerequisites:**
>   - background knowledge of TiDB components
>   - AWS account
>   - deployed TiDB cluster
> - **Optionality:** Required
> - **Estimated time:** TBD


# Scale Out
To scale the TiDB cluster, modify the `default_cluster_tikv_count` or `default_cluster_tidb_count` variable in the `variables.tif` file to the desired count. For example, to scale out the TiDB nodes, you can modify the number of TiDB instances from 2 to 4:

```
default_cluster_tidb_count = 4
```

Then run terraform apply to scale out the number of the corresponding component nodes.

```
$ terraform apply
```

After the nodes scale out, modify the `spec.tidb.replicas` in `TidbCluster` to scale out the Pod.
```
kubectl edit tc ${cluster_name} -n ${namespace}
```

Scaling out needs a few minutes to complete, you can watch the scaling out progress by 
```
kubectl --kubeconfig get po -n ${namespace} --watch.
```

# Scale In

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**NOTE**

Currently, scaling in is NOT supported because we cannot determine which node to scale in.

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