You support a production service that runs on a single Compute Engine instance.

File a bug with the development team so they can find the root cause of the crashing instance.

Create a Managed Instance Group with a single instance and use health checks to determine the system status.

Add a Load Balancer in front of the Compute Engine instance and use health checks to determine the system status.

Create a Stackdriver Monitoring dashboard with SMS alerts to be able to start recreating the crashed instance promptly after it has crashed.