Meilin Data was blamed by some internet users for the crash on December 20. The company responded by saying that it provided algorithm, not operational services.
Dongruan were involved in platform software and customized development services. The platform was originally not designed for displaying the results of mass Covid-19 antigen tests on the app. After the first breakdown, the capacity was expanded to 40,000 QPS (Queries Per Second). However, it was still not enough when all 12 million residents were tested within two days.    
Official Suspended from Office Liu Jun, the head of Xi’an Big Data Resources Administration, apologized for the December 20 breakdown and cautioned residents not to use the app unnecessarily.
His advisory provoked a wave of online mocks. After all, who would use the app when not needed? One netizen said sarcastically: “Don’t show your barcode when you don’t have to; But when you have to, the barcode is dead.”
Liu also gave the reason for the systematic glitch. Too many users were using it at the same time, he said.
As to the cause of the January 4 breakdown, the authorities attributed to “a sudden surge in the number of users”, which was ten times as high as that in the pre-December 9 period. The unusually high volume of visitors led to “online overcrowding,” which triggered the firewall to block information packages. The core issue is that the architecture is not suited for a large number of simultaneous visits.
On January 5, Liu was publicly reproached by Xi’an Municipal Committee of the Communist Party of China in the wake of two breakdowns in two weeks. He was suspended from his position and ordered to hand in a self-criticism report.
According to public information, the “One Barcode to Anywhere” app amassed downloads of over 30 million by over 200,000 stores and companies as well as 50,000 operators and users of the subway system, buses and taxies. The app has been used for a total of 3 billion times in 43,000 neighborhoods. The app, along with big data, has been applied to conduct contact tracing of nearly 400,000 persons and for over 400,000 Covid-19 tests or vaccinations per day.  
Alibaba Not to Blame?Some netizens pointed fingers at Alibaba Cloud after the two crashes. Alibaba Cloud appeared not only on the list of suppliers for the “One Barcode to Everywhere” app, but also on the list of suppliers for “Administrative Cloud.”  
A source close to the procurement project told TMTPost that Alibaba Cloud made a mistake in the analysis of DNS, or Domain Name Service. There are two VIP routes reserved for the app but one error occurred on one of the two routes. RDS, or Relational Database Service, contains many slow SQLs, which caused traffic congestion. The two problems were quickly solved in the wake of the breakdown.  
However, a spokesman of Alibaba Cloud denied the existence of two issues. “Alibaba Cloud provided underlying structure to the “One Barcode to Everywhere” app, but was not involved in the creation of architecture. During the Covid-19 outbreak in Xi’an, Alibaba Cloud platform has been running smoothly. There were no glitches in either DNS analysis or RDS. Our technical team has been on the spot. Alibaba Cloud is willing to make more contributions to the fight against the novel coronavirus,” he said.
An expert in cybersecurity and information technology told TMTPost on the condition of anonymity that traffic congestion triggered a blockage on the firewall and consequently failures of requests for the data. Therefore the personal information of users could be matched with the information on test results or travel history in the cloud, resulting in the failure of information display on a user’s app. Ultimately it was a problem of archteicture, not the firewall, he added.
【{调取该文章的TAG关键词}|Behind the Collapse of Xi'an Covid-19 App】