Abstract: A method for improving the availability characteristics of a constant throughput system that generates scores for multiple resources within multiple nodes in a software stack during a full stack update is disclosed. Each score includes at least a first weighted portion corresponding to a cost of bringing a resource offline, and a second weighted portion corresponding to a cost of re-routing service requests around the resource. An operating system (OS) selects a first node that has a lowest total score, re-routes service requests away from the resources of the first node, and brings the first node offline. The OS updates software of the resources in the first node with minimal disruption and brings the first node back online. The OS re-calculates the scores for the resources, and the OS selects a second node that has a new lowest total score. The OS repeats the process until all nodes are updated.