Kube-State-Metrics is a Kubernetes addon that generates and serves metrics about cluster objects, allowing DevOps teams to detect unhealthy workloads. It's essential for stable Kubernetes operations at scale and provides insights into the states of objects in your cluster. Kube-State-Metrics can be installed using Helm or plain Kubernetes manifest files, and it's maintained as part of the official Kubernetes project. The tool reports metrics about object-level data, such as replicas and pod status, making it useful for monitoring desired versus actual state. It exposes metrics in Prometheus format via an HTTP API, allowing users to consume the data by running Prometheus queries or configuring alerts with Alertmanager. Kube-State-Metrics supports horizontal sharding for improved performance at scale, assigning correct RBAC permissions, using Alertmanager for notifications, and configuring metric allow and deny lists to block unwanted noisy metrics. It's recommended to use it in all production clusters as part of a complete Kubernetes monitoring strategy that also includes solutions like Metrics-Server or Prometheus' Node-Exporter. Spacelift can help manage Kubernetes easier and faster by automating, auditing, securing, and continuously delivering infrastructure.