I've worked with a few companies where it was common practice for developers to work on more than one project concurrently. Guess what, parallel software development doesn't deliver projects more quickly, even if they're small projects. Task switching from one project to another incurs a cost in the form of a time penalty and impacts productivity. When there are a number of projects to complete using the same resources, they'll be delivered more quickly and usually with better quality if they're developed sequentially.
In Lean software development task-switching is waste. Every time a developer switches between tasks, about 15 minutes is required to enter the flow of the new task. When frequently interrupted, frustration kicks and more time is required to calm down and become settled once again. If a developer is working in a group or pair programming there's a productivity boost due to binding and working on a common goal. This is lost when one of the developer's switches tasks. In his book Slack, Tom DeMarco defines the penalty of task switching as:
Task-switching penalty = Mechanics of moving to a new task + Rework due to an inopportune abort + Time to enter flow + Time to defuse frustration + Loss of group binding effect
Task switching increases busyness but most of it is thrashing, non-productive and ineffective work.
Previous Topic
