When (if at all) is it okay to break the WIP limit?

Question

Let's assume that I have a kanban board that has a "Test" column with a WIP limit of x. In the general case, I should not add a card to this column until there is a free space -- at least one card has moved to "Done". Instead, I should give as much help to whomever so that the card currently there can be progressed so they move onwards.

Now, in our case, we have to wait for hardware so no matter how many bodies, as long as the hardware is not ready, we cannot progress this. The way we deal with this is to have a limitless WIP swim lane that hold such stalled cards.

Is this reasonable? Is there a better way?

Answer 1

Is this reasonable?

In my personal experience the answer to that is no. WIP limits exist for a number of very good reasons, one of which is to identify bottlenecks such as that which you have described.

If the hardware is necessary for the HW testing to be completed then by creating a swimlane with limitless WIP you're establishing something of a false economy. It may look as though things in preceding columns are progressing in the short term but once the hardware comes in, those stalled cards will need to be completed and the progress you've established is going to suffer, as you pull all available resources to complete the subsequent columns, or your allocated resources for the later columns will be overwhelmed.

The identification of bottlenecks such as this is not intended to be a paper exercise only, you have the evidence of the bottleneck and now action should be taken (by whomever has the ability e.g. management) to resolve it.

If this is a one-off project then the method you've described is as good as any I can think of to address the issue, just be sure that you're forward planning how you're going to deal with the backlog.

Answer 2

Adding a "Waiting on Hardware" zone at the bottom of your Testing column could be a workable approach. It would allow you keep you WIP limit as a firm limit while still showing the backlog in the correct area of responsibility. Color coding the overhang/delayed demand to highlight it for everyone is probably a good idea. In a way, you are moving it off the board for a while.

However, I could not find examples of people using this approach. It would probably be a bit of experiment.

Answer 3

You could add a column without WIP Limit in front of the test column.

Example for columns TODO | Implementation | Implementation Done | Test | Done

The item would then rest in Implementation Done until the HW arrives and someone picks it up. This state would also be highlighted in some way. We use different Magnets on our board: Colors/Symbols - Team member; White - Neutral Zone (ToDo, Implementation Done); Red - Don't Pick it up