How to Scale ASP.NET Core SignalR Apps

Real-time web applications require efficient communication between clients and servers. ASP.NET Core SignalR simplifies this communication by enabling real-time messaging. It is widely used in chat applications, collaborative editing tools, stock trading platforms, live sports updates, and IoT dashboards, where instant data updates are critical for a smooth user experience.

However, in a scenario where thousands of users are interacting in a chatroom or monitoring real-time analytics, a single server will struggle with connection management and data distribution. To overcome this bottleneck SignalR backplane is used to synchronize messages between them. This is where NCache comes in as a high-performance, distributed caching solution that ensures seamless scalability and real-time message delivery across a web farm.

Challenges in Scaling SignalR with ASP.NET Core

SignalR operates efficiently in a single-server environment, managing connections and real-time message delivery efficiently. However, when applications scale out across multiple servers, several challenges arise, some of which are described below:

Connection Affinity Issues – SignalR uses WebSockets or other transport mechanisms to establish persistent connections. In a multi-server environment, load balancers may distribute clients across different servers, causing message synchronization issues.
Message Loss and Inconsistency – A client connected to one server may not receive messages sent from another server since SignalR does not natively synchronize messages between multiple servers.
Increased Latency – Without a backplane, servers have to handle messaging independently, which can lead to delays and put unnecessary strain on them.
Performance Bottlenecks with Traditional Solutions – While SQL Server has been used as a backplane, but it introduces significant latency and struggles with high message volumes, making it an unsuitable option for real-time applications.

A distributed backplane ensures real-time message synchronization across multiple servers. Instead of each server managing its own connections, the backplane creates a shared communication channel, ensuring all connected clients receive message updates instantly. This minimizes latency, prevents message loss, and supports horizontal scalability. For high-frequency applications like financial trading and multiplayer gaming, a distributed backplane is essential for delivering consistent and reliable performance.

Why Use NCache as a SignalR Backplane?

NCache is an in-memory distributed caching solution that ensures real-time message synchronization across multiple SignalR servers. Using NCache as a distributed backplane allows web applications to scale horizontally without sacrificing real-time communication, availability, or performance.

The following characteristics of NCache makes it an ideal choice to be used as a backplane:

Highly Performant & Scalable – NCache scales linearly, allowing seamless expansion as demand increases, while its in-memory architecture ensures ultra-low latency leading to improved performance.
Reliable & Efficient Data Replication – To ensure resilience against failures NCache replicates data across cache nodes.
Native .NET Support – Fully compatible with .NET applications, making it a natural fit for ASP.NET Core SignalR.
Real-Time Pub/Sub Messaging – Provides robust publish/subscribe capabilities for efficient message broadcasting across web servers.
Optimized for SignalR Groups & Users – Supports seamless messaging to groups and targeted user connections.
Persistent Connections & Two-Way Invocation – Maintains active connections and enables two-way method invocation between clients and servers.
Reliable Message Transport – Combines a built-in transport layer with guaranteed message delivery, ensuring seamless and consistent communication across all connected clients.

By integrating NCache as a backplane, SignalR applications achieve real-time scalability with minimal configuration, delivering a responsive and seamless user experience.

Implementing NCache as a SignalR Backplane

Integrating NCache with your ASP.NET Core SignalR application is straightforward and requires minimal code changes. Follow these steps to configure NCache as a SignalR backplane:

1. Install the NCache SignalR NuGet Package

Add the NCache SignalR package to your project using the following command:

1	Install-Package Alachisoft.NCache.SignalR

2. Modify appsettings.json

Define your NCache configuration settings in appsettings.json:

{

"Cache": "demoCache"

"EventKey": "Chat"

}

3. Register NCache as a SignalR Backplane

Modify Startup.cs to configure SignalR to use NCache as a backplane:

using Alachisoft.NCache.SignalR;

using Microsoft.AspNetCore.SignalR;

using Microsoft.Extensions.Configuration;

public class Startup

{

public void ConfigureServices(IServiceCollection services)

{

string cache = Configuration["Cache"];

string eventKey = Configuration["EventKey"];

services.AddSignalR()

.AddNCache(cache, eventKey);

}

4. Deploy and Scale

Once configured, deploy your application across multiple web servers, and NCache will automatically handle message synchronization between them.

Performance Benefits of NCache as a SignalR Backplane

Using NCache provides several performance advantages over other backplane solutions:

Feature	NCache	SQL Server
Scalability	Linear scaling	Limited scaling
Latency	Low latency	High latency
Reliability	High availability	Prone to bottlenecks
Native .NET Support	Yes	Yes

Conclusion

To handle high traffic and ensure smooth real-time messaging across multiple servers, scaling ASP.NET Core SignalR applications efficiently is essential. NCache provides a fast, scalable, and reliable backplane eliminating bottlenecks and boosts overall performance.

By integrating NCache as a SignalR backplane, developers can achieve real-time messaging at scale with minimal configuration changes. Whether you’re building a chat application, financial trading platform, or collaborative tool, NCache ensures a seamless and highly responsive experience for your users.

For more details, refer to the official NCache documentation.