Each request carries some data over the network; if the request does not find any updates on the server, this datatransfer is a waste.
每一次请求都要在网络上传输一些数据;如果请求未在服务器上发现任何更新,那么这个数据传输就是浪费的。
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On the top of that, each request carries some data over the network; if the request does not find any updates on the server, this datatransfer is a waste.