As mentioned in Schema and data model, you should be careful when choosing a primary key to not accidentally create hotspots in your database. One cause of hotspots is having a column whose value monotonically increases as the first key part, because this results in all inserts occurring at the end of your key space. This pattern is undesirable because Cloud Spanner divides data among servers by key ranges, which means all your inserts will be directed at a single server that will end up doing all the work.https://cloud.google.com/spanner/docs/schema-design#primary-key-prevent-hotspots

Keywords: - continually -> Standard - mission-critical analytics -> dual-regional

https://cloud.google.com/compute/docs/instance-groups
https://cloud.google.com/load-balancing/docs/network/transition-to-backend-services#console
* In order to enable auto-healing, you need to group the instances into a managed instance group.
Managed instance groups (MIGs) maintain the high availability of your applications by proactively keeping your virtual machine (VM) instances available. An auto-healing policy on the MIG relies on an
* application-based health check to verify that an application is responding as expected. If the auto-healer determines that an application isnt responding, the managed instance group automatically recreates that instance.
It is important to use separate health checks for load balancing and for auto-healing. Health checks for load balancing can and should be more aggressive because these health checks determine whether an instance receives user traffic. You want to catch non-responsive instances quickly, so you can redirect traffic if necessary. In contrast, health checking for auto-healing causes Compute Engine to proactively replace failing instances, so this health check should be more conservative than a load balancing health check.

Reference:
https://cloud.google.com/compute/docs/disks/performance