# CBDDC Deployment Mode

ZB.MOM.WW.CBDDC.Hosting supports a single deployment mode.

## Single-Cluster Mode

**Best for:**
- Dedicated database servers
- Simple deployments
- Development/testing environments
- Small-to-medium applications

### Architecture

```
┌─────────────────────┐
│   ASP.NET Server    │
│                     │
│  ┌───────────────┐  │
│  │    CBDDC      │  │
│  │  (1 cluster)  │  │
│  └───────────────┘  │
│         │           │
│    [TCP:5001]       │
└─────────────────────┘
```

### Configuration

```csharp
builder.Services.AddCBDDCHostingSingleCluster(options =>
{
    options.NodeId = "server-01";
    options.TcpPort = 5001;
});
```

### Characteristics

- One database per server instance
- Simple configuration
- Easy to scale horizontally (multiple servers = multiple databases)
- No port collision issues
- Recommended for most use cases

## Server Behavior

Servers use respond-only operation:

- Accept incoming TCP sync connections
- Respond to sync requests
- Serve data to clients
- Maintain persistence
- Do not initiate outbound sync
- Do not perform UDP discovery
- Do not connect to other servers automatically

## Persistence Layer Compatibility

Single-cluster mode works with all persistence providers:

| Provider | Support | Notes |
|----------|---------|-------|
| SQLite (Direct) | Yes | One DB file per cluster |
| EF Core | Yes | Flexible DB options |
| PostgreSQL | Yes | Best for production |

## Scaling Strategy

### Horizontal Scaling

```
Load Balancer
     │
     ├─> Server 1 (Cluster A) [PostgreSQL A]
     ├─> Server 2 (Cluster B) [PostgreSQL B]
     └─> Server 3 (Cluster C) [PostgreSQL C]
```

## Recommendation

Use single-cluster mode for ASP.NET hosting. It is simpler, robust, and straightforward to scale.