Technical Analysis of the Xi'an Health Code Platform Crash: Backend Bottlenecks and Bandwidth Issues
The article examines the recent Xi'an health‑code system failure, highlighting that the crash stemmed from backend design flaws such as serving all static assets without a CDN, excessive bandwidth demand exceeding 125 Gbps, and inefficient QR‑code API handling.
Recent discussions about the second collapse of Xi'an's "One‑Code‑Pass" platform reveal that the failure was not caused by a simple image‑generation bug but by deeper backend shortcomings.
Analysts note that the system’s static resources—JavaScript, CSS, and images—were all delivered from a single entry point without CDN acceleration, totaling roughly 500 kB per request.
Given peak request volumes of about 33,000 queries per second, the estimated outbound traffic reaches 33000 × 500 kB × 8 bits ≈ 125 Gbps, a load far beyond the capacity of a single data‑center network interface, leading to saturation and complete outage.
Further investigation identified the actual QR‑code generation endpoint as /person/app/refreshQRCode , confirming that the server does not generate images on‑the‑fly but returns QR‑code data directly.
A contributor on Zhihu emphasized that the primary issue lies in the lack of CDN for static assets, which, combined with the massive concurrent traffic, caused the network bottleneck and eventual system crash.
The analysis concludes that while the problem was not the low‑level image handling some rumors suggested, the backend architecture and resource delivery strategy were insufficient for the scale of usage.
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