Cloud servers can cost a lot of money. But there is a smart way to save cash: use Spot Instances (Google calls them Preemptible VMs). They are leftover servers that the cloud provider sells with a huge discount, often up to 90% off. The only problem? The cloud provider can take them back with almost no warning if a full-paying customer needs them. Because of this risk, you cannot run your whole website or app on Spot servers. If they disappear, your app crashes. You need a mi