The four key flow metrics in Scrum with Kanban are:

* Work in Progress (WIP): The number of items that are currently being worked on.

* Work Item Age: The time that has elapsed since an item started, which helps identify aging work that may need attention.

* Throughput: The number of items completed over a specific period, helping to measure productivity.

* Cycle Time: The total time from when an item starts until it is finished, used to assess how quickly items are moving through the process.

These metrics are essential for understanding and optimizing the flow of work in a Scrum team using Kanban practices