hchoang's blog

By Cat Hoang April 20, 2026

Demystifying the Architecture of a Million-User Live Chat System: Why WebSockets Aren’t Always the Answer

When software engineers think about real-time chat applications, 90% immediately lean toward WebSockets. This protocol establishes a persistent, bi-directional (full-duplex) connection between the client and server, allowing data to flow back and forth instantly. However, for massive live streaming platforms hosting millions of concurrent viewers, maintaining millions of open WebSocket connections simultaneously is incredibly expensive […]

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By Cat Hoang March 26, 2026

Why Google, Facebook, and Canva Inject “Junk Characters” into API Responses

If you have ever poked around the Network tab in your browser’s Developer Tools while using services from tech giants like Google, Meta (Messenger), or Canva, you might have stumbled upon something bizarre. Right at the beginning of their JSON API responses, they often insert a few strange, invalid characters (like )]}’,), or even an […]

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By Cat Hoang February 15, 2026

How YouTube Counts Live Viewers (Without Using WebSockets)

If you have ever tuned into a massive product launch, a gaming tournament, or a breaking news broadcast on YouTube, you have probably noticed the real-time viewer count fluctuating under the video. Updating that metric accurately for millions of concurrent users across the globe is a massive system design challenge. The immediate technical instinct for […]

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