One queue shrinks while the customer waits longer
A fictional IT-service team changes its workflow to close local tasks faster. Supplied measurements show that its own active processing time fell, but handoffs and the next team’s waiting queue grew, leaving overall customer lead time worse. A colleague proposes declaring Lean success because one team’s utilization improved. Another maps the full demand-to-delivery stream and asks for consistent lead-time, WIP, throughput and quality observations. No board or staffing change occurs in this written exercise. The learner must distinguish local activity improvement from end-to-end service value and explain how a bounded follow-up test can preserve necessary controls while addressing the actual bottleneck and downstream effect.
1. Why is local processing time not enough?
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The customer’s outcome spans the whole stream. Increased waiting and handoffs can outweigh a local speed improvement, so the stated overall result does not support the success claim.
2. What should the review test?
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Use consistent end-to-end flow/quality measures and actual queue evidence, identify a justified bottleneck hypothesis and test a narrow change with accountable ownership and downstream verification.