A traditional approach is to create a "heartbeat" system where a lightweight AJAX "HEAD" request is sent every 15 seconds, with the server signaling in the reply header that there is new content available.
Once the indication is received, the application can then fetch the additional data. It's possible to combine these two steps into one request, especially for frequently changing data.
This method may seem like an "infinite loop," but it actually involves using repeated setTimeout() calls instead of setInterval(). This ensures waiting for a response or timeout before sending another request, avoiding potential complications and headaches.
Keep in mind that as the application's traffic increases, so will the number of requests to the server. Each request should be secure yet lightweight, with the server implementing caching measures to minimize frequent database calls during each heartbeat check.
Although this traditional technique is widely used, newer technologies are at developers' disposal:
For instance, developers can explore utilizing WebSockets, or for those working with asp.net, Microsoft's SignalR offers a comprehensive solution that blends multiple technologies and ensures compatibility across various browsers and devices.