https://e-mahmoudi.me/tags/scalability/Recent content in Scalability on Ehsan Mahmoudi — Blockchain Consultant & Software Architect | Hire RemoteHugoen-usSun, 16 Aug 2026 00:00:00 +0000https://e-mahmoudi.me/blog/fanout-architecture-millions-concurrent-websockets/Sun, 16 Aug 2026 00:00:00 +0000https://e-mahmoudi.me/blog/fanout-architecture-millions-concurrent-websockets/<h1 id="how-fanout-broadcasting-powers-millions-of-concurrent-websocket-connections">How Fanout Broadcasting Powers Millions of Concurrent WebSocket Connections</h1> <p>I&rsquo;ve been working on a chat platform that handles millions of concurrent public chat participants. Early on, I faced the fundamental question every real-time platform asks:</p> <blockquote> <p>How do you broadcast a single message to 10,000 people on the same chat simultaneously, across multiple servers, without everything collapsing?</p> </blockquote> <p>The answer turned out to be simpler than I expected. Not simpler in implementation—the implementation is thoughtful—but simpler in <em>concept</em>. The pattern is called <strong>fanout broadcasting</strong>, and I want to walk through it because it&rsquo;s one of those designs where understanding the shape immediately makes you understand why it scales.</p>