Work in Progress
There is only one management criteria used by Kanban: Work in Progress (WIP).
By managing WIP, the team will be able to optimize the flow of work items. Every column (state) of the Kanban board should define a WIP Limit, so that the team knows how many work items can be in each column at the same time. This way it is easy to see if there is any bottleneck and the progress of the workload is always visible.
Since in Kanban methodology the flow is continuous, there are no roles and no product iterations, so it is based on continuous delivery (or agreed by the team) and changes are welcome at any moment. Continuous Improvement is the basic principle of Kanban thanks to the wide visibility of all the workflow at any time and the quick detection of impediments and bottlenecks.