[Front End] How can Taobao’s shopping cart control the disabling and enabling of the [Settlement] button in milliseconds under the condition of high concurrency? What technologies did he use at the front end?

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How does Taobao’s shopping cart achieve high concurrency while still ensuring merchandiseReal timeIt indicates that the goods are in stock and out of stock, which is effectively invalid, and then controls the disabling and enabling of the [Settlement] button. What technologies did he use at the front end?

When I was robbing the explosion models, I found that they were out of stock, but I refreshed them again and again. Sometimes I could see that the explosion models were in stock, but when I clicked the check box, they were out of stock immediately, or the settlement button could not be clicked for a short time, and then they were out of stock instantly.

This front-end control (real-time communication between the front-end and the server), which is almost accurate to millisecond level, can be so accurate under high concurrency. How is this achieved? Do you have any predecessors or heroes to analyze?

NoSQL cache layer