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

Question

Ravi Vishwakarma · Answer

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?
SignalR stores connection info in-memory per server, so by default:
A message sent on Server A won't reach a client connected to Server B.Redis solves this by syncing messages across servers.
and 
Steps to Set Up SignalR with Redis Backplane
1. Install Redis and Required NuGet Package
Install the Redis backplane package:
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:
public void ConfigureServices(IServiceCollection services)
{
    services.AddSignalR().AddStackExchangeRedis("localhost:6379", options =andgt;
    {
        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.
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:
You’re hosting your app on multiple servers/instances.You need reliable group messaging across instances.You want to scale horizontally with a load balancer.
What Redis Backplane Does Not Do
It does not share connection state — it just forwards messages.You still need to re-add group memberships on reconnect.It does not persist messages (not a message queue).
Additional Tips
Use a load balancer with sticky sessions (optional) for more predictable connection mapping.For high-scale production, consider:
Azure SignalR Service (fully managed)Scaling Redis (using Redis Cluster or Sentinel)

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

Ravi Vishwakarma

Can you answer this question?

1 Answers

Why Use a Redis Backplane?

Steps to Set Up SignalR with Redis Backplane

1. Install Redis and Required NuGet Package

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

3. Use SignalR as Usual

When to Use Redis Backplane

What Redis Backplane Does Not Do

Additional Tips

Liked By

interview

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

Ravi Vishwakarma

Can you answer this question?

1 Answers

Why Use a Redis Backplane?

Steps to Set Up SignalR with Redis Backplane

1. Install Redis and Required NuGet Package

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

3. Use SignalR as Usual

When to Use Redis Backplane

What Redis Backplane Does Not Do

Additional Tips

Liked By

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