---
title: "How do you scale a SignalR application across multiple servers (e.g., using Redis backplane)?"  
description: "How do you scale a SignalR application across multiple servers (e.g., using Redis backplane)?"  
author: "Ravi Vishwakarma"  
published: 2025-05-22  
updated: 2025-05-22  
canonical: https://www.mindstick.com/interview/34157/how-do-you-scale-a-signalr-application-across-multiple-servers-e-g-using-redis-backplane  
category: "c#"  
tags: ["c#", "signalr"]  
reading_time: 4 minutes  

---

# How do you scale a SignalR application across multiple servers (e.g., using Redis backplane)?

To **scale a SignalR application across multiple servers**, you need to share connection state and messages between instances. This is done using a **backplane**, with **Redis** being the most popular and efficient choice.

## Why Use a Redis Backplane?

1. SignalR stores connection info **in-memory per server**, so by default:

   1. A message sent on Server A won't reach a client connected to Server B.
   2. Redis solves this by syncing messages across servers.

##

## Steps to Set Up SignalR with Redis Backplane

### 1. Install Redis and Required NuGet Package

Install the Redis backplane package:

```cs
dotnet add package Microsoft.AspNetCore.SignalR.StackExchangeRedis
```

Ensure you have a Redis server running (locally, on Docker, or hosted).

### 2. Configure SignalR to Use Redis in `Startup.cs` (or `Program.cs`)

For ASP.NET Core:

```cs
public void ConfigureServices(IServiceCollection services)
{
    services.AddSignalR().AddStackExchangeRedis("localhost:6379", options =>
    {
        options.Configuration.ChannelPrefix = "MyAppSignalR"; // optional, for multiple apps
    });

    // ... other services
}
```

> Replace `localhost:6379` with your actual Redis connection string.

### 3. Use SignalR as Usual

No changes needed in your `Hub` code or client code — Redis handles syncing behind the scenes.

```cs
public class ChatHub : Hub
{
    public async Task SendMessageToRoom(string roomName, string message)
    {
        await Clients.Group(roomName).SendAsync("ReceiveMessage", Context.UserIdentifier, message);
    }
}
```

## When to Use Redis Backplane

Use Redis if:

1. You’re hosting your app on **multiple servers/instances**.
2. You need **reliable group messaging across instances**.
3. You want to scale **horizontally** with a load balancer.

## What Redis Backplane Does Not Do

1. It **does not share connection state** — it just **forwards messages**.
2. You still need to **re-add group memberships on reconnect**.
3. It does **not persist messages** (not a message queue).

## Additional Tips

1. Use a **load balancer** with **sticky sessions (optional)** for more predictable connection mapping.
2. For high-scale production, consider:

   1. **Azure SignalR Service** (fully managed)
   2. **Scaling Redis** (using Redis Cluster or Sentinel)

## Answers

### Answer by Ravi Vishwakarma

To **scale a SignalR application across multiple servers**, you need to share connection state and messages between instances. This is done using a **backplane**, with **Redis** being the most popular and efficient choice.

## Why Use a Redis Backplane?

1. SignalR stores connection info **in-memory per server**, so by default:

   1. A message sent on Server A won't reach a client connected to Server B.
   2. Redis solves this by syncing messages across servers.

##

## Steps to Set Up SignalR with Redis Backplane

### 1. Install Redis and Required NuGet Package

Install the Redis backplane package:

```cs
dotnet add package Microsoft.AspNetCore.SignalR.StackExchangeRedis
```

Ensure you have a Redis server running (locally, on Docker, or hosted).

### 2. Configure SignalR to Use Redis in `Startup.cs` (or `Program.cs`)

For ASP.NET Core:

```cs
public void ConfigureServices(IServiceCollection services)
{
    services.AddSignalR().AddStackExchangeRedis("localhost:6379", options =>
    {
        options.Configuration.ChannelPrefix = "MyAppSignalR"; // optional, for multiple apps
    });

    // ... other services
}
```

> Replace `localhost:6379` with your actual Redis connection string.

### 3. Use SignalR as Usual

No changes needed in your `Hub` code or client code — Redis handles syncing behind the scenes.

```cs
public class ChatHub : Hub
{
    public async Task SendMessageToRoom(string roomName, string message)
    {
        await Clients.Group(roomName).SendAsync("ReceiveMessage", Context.UserIdentifier, message);
    }
}
```

## When to Use Redis Backplane

Use Redis if:

1. You’re hosting your app on **multiple servers/instances**.
2. You need **reliable group messaging across instances**.
3. You want to scale **horizontally** with a load balancer.

## What Redis Backplane Does Not Do

1. It **does not share connection state** — it just **forwards messages**.
2. You still need to **re-add group memberships on reconnect**.
3. It does **not persist messages** (not a message queue).

## Additional Tips

1. Use a **load balancer** with **sticky sessions (optional)** for more predictable connection mapping.
2. For high-scale production, consider:

   1. **Azure SignalR Service** (fully managed)
   2. **Scaling Redis** (using Redis Cluster or Sentinel)


---

Original Source: https://www.mindstick.com/interview/34157/how-do-you-scale-a-signalr-application-across-multiple-servers-e-g-using-redis-backplane

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