What is a Bottleneck?
In the simplest definition, a process bottleneck is a work stage that gets more work requests than it can process at its maximum throughput capacity. That causes an interruption to the flow of work and delays across the production process.
In other words, even if this work stage operates at its maximum capacity, it still can’t process all of the work items quick enough to push them to the next stages without causing a delay.
The workflow bottleneck can be a computer, a person, a department or a whole work stage. Typical examples of bottlenecks in knowledge work are the software testing and quality review processes.
Unfortunately, a bottleneck is often acknowledged only after it has caused a blockage in the workflow.
How to Detect a Workflow Bottleneck?
If you see that your workflow is unpredictable and operates in bursts, instead of a smooth flow, you have a bottleneck somewhere.
The real issue lies in pinpointing it and setting an appropriate countermeasure. In Lean Management, to detect a bottleneck, you can use several Kanban bottleneck analysis tools.
Here is how to identify a bottleneck in 3 steps:
- Visualize. Keeping track of your work in the form of task cards on a Kanban board makes it very easy to see where work items pile up, which is a strong sign of a problem, most likely a bottleneck.
- Map Queues and Activities. When we separate queues and activities and map them on the Kanban board, we can see how much time our work sits waiting in a queue prior to a certain activity. If this queue grows significantly faster than the activity stage processes work, you have found your bottleneck.
- Measure Cycle Time per Stage. Measuring cycle time at every stage lets you build a cycle time heat map diagram. Just a glance at this diagram reveals the stages where cards spend the most time. If these workflow stages are queues too, those are probably your bottlenecks.
What to do next? How to deal with a bottleneck?
At times, you can easily resolve the bottleneck by allocating more resources or people to that work stage or process. That could mean hiring one more QA tester for the sake of a more streamlined production flow.
However, what if the bottleneck requires a particularly scarce resource or hard-to-find expertise? In some cases, the cost of the solution to the bottleneck can be too high.
Leaving a bottleneck untreated will always cost you more than resolving it.
What should you do next then?
Here are several things you should do to contain the bottleneck:
- Never leave it idle. Because of the ripple effect that it has on the rest of the flow, the bottleneck process should always be loaded at full capacity.
- Reduce the strain on the bottleneck. Make sure that work arrives at it in its very best form. If your review process is a bottleneck, ensure that the quality is built in from the start. The work to be reviewed has to be flawless, each error that the reviewer finds is going to cost you more time and money.
- Manage WIP limits. If the work in progress limits are quite liberal in the bottleneck and there is a lot of context switching, consider lowering the WIP limit. If it doesn’t have a WIP limit, consider setting one.
- Process work in batches. Some of the operations would take less time if you organized similar work items in batches. However, be cautious, the larger the batch size is the higher is the risk. The rule of thumb is that a smaller batch is always better, but in the real world, we sometimes have to make compromises.
- Add more people and resources. If you can, increase the capacity of the bottleneck in order to speed up the whole process. However, keep your eyes wide open, as soon as the resources in the system are re-distributed, another bottleneck is bound to appear elsewhere in the system.
Continuous Bottleneck Analysis With Kanban
The key to a healthy and productive Flow is the absolute minimum interruption to the process, the work has to stream through it freely powered by the Pull power.
Following the Lean management concept of continuous improvement, bottleneck analysis should also be an ongoing process.
After all, in the modern ever-changing markets, every time the relative balance in the production system is disturbed, you will need to review the workflow to see if any new congestions occurred and what needs to be done to reduce their effect.
Get your work under control with Kanban workflows and Lean bottleneck analysis tools to reach an unprecedented level of flow predictability.