Where can Scrum not be used?

Amid much debate over the usefulness of Scrum, it’s useful to ask where can Scrum *not* be used?  If it’s hard to define what something is good for, it may be easier to define what it isn’t.

So where shouldn’t we use Scrum?

Where priorities change hourly or daily.

Where unplanned work is a significant part of the workload.

Where teams are unstable, swarming to work.

Where work planning is not product-based.

Where there is poor demand management.

Where… In many contexts.

I’m no expert, not highly experienced, but it feels to me that Kanban best models the VUCA nature of reality, whereas Scrum only works in a well-bounded well-defined disciplined flow.

So where *should* we use Scrum? If flow of work is steady, prioritized, and fairly predictable; demand is well managed; and the dependencies in the system are challenging so we work on bigger lumps of work at a time; then Scrum on!