Server-to-client messaging

[nssidhu]

Planning to create Blazor WebAssembly PWA application with Asp.net Core back end. I want to understand which option of sending message from server to client would be best.

1. SignalR
   It keeps live connection between server(ASP.net Core) and client(Blazor WebAssembly PWA app).
   It is good for few hundred concurrent connection
2. Polling
   Client polls the server to check if there are any message for itself and get more details if any
   Will handle maximum number of concurrent connection depending on Server/Backend sizing
3. Push service
   I don't prefer it as it is complicated one to implement, the message should be received and reacted by application instead
   of browser.

I want the solution to be stateless, not hold on to the connection, so that it can allow thousands of client and be the cheapest
as the same time.

Any guidance with the limitations on concurrent user handling and cost will be appreciated.
Think of this app to be on the scale like WhatsApp, except it is more on the Server to Client communication, instead of client to client like in WhatsApp.