现在，我们谁也不想陷入进不了自己家门的境地，但请务必花点时间想一想，把备用钥匙放在哪里才是最好、最安全的地方。

Now, none of us want to be in the situation where we can't get into our own home, but do take time to think where the best and safest place is to leave your spare keys.

youdao

在最简单的情况下，每台服务器配备一台备用服务器，用于故障恢复。

In the simplest case, a server is paired with a backup that serves as the failover target.

youdao

购物者没钱不能在超市买够东西，只能前往最便利的地方购买紧急时备用应急的食物，如牛奶和鸡蛋。

Shoppers can't afford to load up at the supermarket and are going to the most convenient places to buy emergency food items like milk and eggs.

youdao