A bottleneck is a constraint that creates a backlog around the “bottleneck.” Usually, these constraints prevent the system from achieving more of its goals. There are many ways the constraints can show up. They can be internal or external to the system types and could be a result of equipment, people, policies, or ineffective processes. Identifying constraints and alleviating bottlenecks are often a key objective of business transformation projects.

Source: Guide to the Business Process Management Body of Knowledge – ABPMP BPM CBOK V3.0.

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