How can you ensure a new application instance deployed in a managed instance group is healthy before continuing deployment?

To ensure that a new application instance deployed in a managed instance group is healthy before continuing deployment, it is essential to control the rollout strategy carefully. The choice involving a rolling-action configuration with maxSurge set to 0 and maxUnavailable set to 1 allows for deploying a new instance while maintaining the overall reliability and health of the application.

This approach means that as you introduce one new instance, you allow one existing instance to be temporarily unavailable for testing and validation. This is critical for monitoring the newly deployed instance's health status and ensuring that it functions correctly under load. If the new instance proves to be healthy, the deployment can progress without affecting the overall service availability. Thus, the system can validate the new deployment without overloading or destabilizing the existing instance group.

The configuration prioritizes the stability of the application by not exceeding the count of instances that are available, which helps in scenarios where immediate rollback or further actions may be needed based on the new instance's health metrics.