# Scaling

This page discusses horizontal scaling to meet increasing demands.

The page does not cover scaling services such as Kafka, Zookeeper, and PostgreSQL Metrics.

### Horizontal Scaling of ESS

Horizontal scaling of ESS involves adding more worker nodes (VMs) to run additional instances of ESS services; for instance, having 2 instances of Pod Storage service, each running on a separate server, instead of a single Pod Storage service running on one server.

### Scale Services Independently

With ESS, you can scale each service independently of each other. For example, you can have 3 instances of the Pod Storage service and 1 instance of the [Solid OIDC Broker Service](https://docs.inrupt.com/ess/2.5/services/service-oidc).

### Stateless Services

All user-facing ESS services (Pod Storage, etc.) are stateless. Using stateless services strongly supports horizontal scaling as a user’s requests to a given service do not need to route to the same instance of that service.

### Scale a Deployment

You can use [Kustomize Overlays](https://kubernetes.io/docs/tasks/manage-kubernetes-objects/kustomization/#bases-and-overlays) to scale your deployment.

### Example: Scale a Deployment

Adding more Pod provisioning helps with resiliency. The following example file sets the number of replicas for **`ess-pod-provision`** deployment to **`2`** .

1. Go to your ESS installation directory:

   ```sh
   cd ${HOME}/ess
   ```
2. Modify the **`kustomization.yaml`** (i.e., step 3 of the [Applying Your Customizations](https://docs.inrupt.com/ess/installation/customize-configurations#applying-your-customizations) procedure).\
   Specifically, add the highlighted content to the **`kustomization.yaml`** file under the **`replicas`** key:

{% hint style="info" %}
**Tip**\
If **`replicas`** key does not exist in **`kustomization.yaml`** , add the key **`replicas`** as well.
{% endhint %}

<pre class="language-yaml"><code class="lang-yaml">
# kustomization.yaml in your ESS installation directory
# ...  Preceding content omitted for brevity 
# ...
replicas:
<strong>- name: ess-pod-provision
</strong><strong>  count: 2
</strong>
</code></pre>

3. Continue with the rest of the [Applying Your Customizations](https://docs.inrupt.com/ess/installation/customize-configurations#applying-your-customizations) procedure.