Inspecting the Value Stream
This domain tests whether you can read a value stream while it is running: which signals to look at, how often, and how to convert what you see into an action on the constraint.
The constraint sets the pace
Goldratt's Theory of Constraints gives five focusing steps: identify the constraint, exploit it (get more from it without spending), subordinate everything else to its pace, elevate it (add capacity or remove the need), then repeat - and beware inertia becoming the next constraint. In knowledge work the constraint is usually a queue in front of a scarce skill, a single approver, or an environment, not a person's effort.
What to inspect
- Aging WIP: how long current items have been in progress. It is the earliest warning that a queue is growing.
- Queue size and blocked items at each step.
- WIP against stated limits.
- %C&A and rework loops.
- Lead-time percentiles, throughput trend, and flow distribution across work types.
Cadence and behaviour
A common pattern: a daily team-level flow check on aging items and blockers, a weekly or biweekly value stream review with the value stream owner across all steps, and a periodic re-map. Inspect the flow, not the people; the review exists to remove blockers, not to report status.
Worked example
A stream holds throughput steady at eight features per week, but lead time climbs from 15 to 28 days. The aging WIP report shows 40 items waiting more than ten days in security review, served by one part-time reviewer at 95% utilization. The reasoning: throughput has not fallen, so the growth is queue, and by Little's Law the rising WIP explains the rising time. The response exploits the constraint first - automated policy checks plus a fixed daily review slot - and only elevates with a second reviewer if the queue persists after that.
Traps that cost marks
- Turning the review into a status meeting.
- Optimizing a step that is not the constraint, which only builds inventory.
- Treating the constraint as permanent; after it is elevated, re-identify it.
- Inspecting only delivery and ignoring the discovery and feedback stages.