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

# Overview

> Understanding apps in EnSync

## What Are Apps?

Apps in EnSync represent your services or applications that publish and subscribe to events. Each app has unique credentials for authentication and encryption.

## App Components

Every app consists of three key components:

| Component     | Type              | Purpose                                   |
| ------------- | ----------------- | ----------------------------------------- |
| **appId**     | Public identifier | Identifies your app in the EnSync network |
| **appKey**    | Secret credential | Authenticates your SDK client connections |
| **appSecret** | Private key       | Decrypts events sent to your app          |

## Creating Apps

Apps are created in the EnSync Dashboard or programmatically via the API.

When you create an app, you receive:

* appKey (for authentication)
* appId (public identifier)
* appSecret (for decryption)

See [Create Access Key](/api-reference/endpoint/access-keys/create) in the API Reference for programmatic creation.

## How Apps Work

### Publishing Events

When you publish an event, you specify recipient appIds:

```javascript theme={null}
await client.publish(
  "order/created",
  ["partner-app-id-1", "partner-app-id-2"],
  { orderId: "123", amount: 99.99 }
);
```

EnSync encrypts the event for each recipient using their appId.

### Subscribing to Events

Your app subscribes to events using its appKey:

```javascript theme={null}
const client = await EnSyncClient.create({
  appKey: "your-app-key",
  appSecret: "your-app-secret"
});

await client.subscribe("payment/*");
```

EnSync decrypts events using your appSecret.

## App Permissions

Apps have two types of permissions:

* **send**: Event paths this app can publish to
* **receive**: Event paths this app can subscribe to

```json theme={null}
{
  "send": ["order/*", "inventory/*"],
  "receive": ["payment/*", "refund/*"]
}
```

<Note>
  Permissions are enforced by EnSync. Attempting to publish or subscribe to unauthorized event paths will fail.
</Note>

## Multiple Workers

You can run multiple workers (client instances) with the same appKey to scale horizontally. EnSync coordinates event delivery across workers automatically.

```javascript theme={null}
// Worker 1
const client1 = await EnSyncClient.create({ appKey, appSecret });

// Worker 2 (same appKey)
const client2 = await EnSyncClient.create({ appKey, appSecret });

// Both workers receive events in parallel
```