Have you ever worked as a cashier before？

ever和before 一个曾经，一个之前，意思不会太重复吗？

为什么经常看到一个句子同时用它们2个呢？

     【答】只用其中一个就够了。语言贵在精炼。例如：Have you ever thought of changing your job？你想过换一下工作吗？...... Have you ever been to Rome ? 你去过罗马吗？（摘自《牛津高阶英汉双解词典》第9版）Have you worked as a cashier before？