Cruise is a node implementation of the Raft consensus algorithm. It's primary use is to coordinate groups of machines within a distributed system. Cruise ensures that nodes will hold a consistent view of the cluster's replicated log. Raft is similar to Paxos, but with the goal of being simpler to implement and understand. For a more complete description, it's worth checking out the original paper by Diego Ongaro and Jon Ousterhout.