In 30 seconds
- Counts items waiting to be worked on at each step.
- Long queues cause delays, stale work and rework.
- Watching queues is one of the earliest warnings of trouble.
Why queues matter
Don Reinertsen's work on product development flow argues that queues are a major hidden cause of delay. Unlike factory inventory, work queues in knowledge work are invisible unless you put them on a board.
Seeing queues
- Add "waiting" or "ready" columns to the board
- Watch band thickness on a cumulative flow diagram
- Count items waiting for review, test or approval
Keeping queues short
- Use WIP limits that include waiting columns
- Reduce batch sizes
- Prune the backlog of items that will never be done
Myth vs reality
Myth · A long backlog is a healthy pipeline.
Reality · It's a queue that ages and wastes refinement.
Myth · Queues mean everyone is busy, which is good.
Reality · Busy systems with long queues are slow.
Myth · Queues are only in development.
Reality · Approvals and handoffs create queues too.
FAQ
How long should a queue be?
Short enough that items don't go stale waiting.
How does queue length affect lead time?
Longer queues mean longer lead times.
What's the quickest win?
Usually limiting work waiting for review.