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One way to minimize computing costs is to use preemptible virtual machines, which are short-lived VMs that cost about 80 percent less than their nonpreemptible counterparts. Here are some things to keep in mind about preemptible VMs when considering business and technical requirements:

 Preemptible VMs may be shut down at any time by Google. They will be shut down after running for 24 hours.

 GCP will signal a VM before shutting down. The VM will have 30 seconds to stop processes gracefully.

 Preemptible VMs can have local SSDs and GPUs if additional storage and compute resources are needed.

 If you want to replace a preempted VM automatically, you can create a managed instance group for preemptible VMs. If resources are available, the managed instance group will replace the preempted VM.

 Preemptible VMs can be used with some managed services, such as Cloud Dataproc, to reduce the overall cost of the service.

Preemptible VMs are well suited for batch jobs or other workloads that can be disrupted and restarted. They are not suitable for running services that need high availability, such as a database or user-facing service, like a web server.

Preemptible VMs are also not suitable for applications that manage state in memory or on the local SSD. Preemptible VMs cannot be configured to live migrate; when they are shut down, locally persisted data and data in memory are lost. If you want to use preemptible VMs with stateful applications, consider using Cloud Memorystore, a managed Redis or memcached service for caching data, or a database to store state.

Google Cloud offers Spot VMs, which are similar to preemptible VMs but do not necessarily shut down within the first 24 hours of running. At the time of writing, Spot VMs are in Pre-GA, may have limited support, and may not be feature complete. Throughout this book, we will use the term Preemptible VMs to refer to low-cost instances that may be provisioned as traditional Preemptible VMs or as Spot VMs.