Interruptions from outside the team happen for any number of reasons. Sometimes they are urgent, sometimes they are not. We want to accommodate them if we can but always being aware that there is always a cost to interruptions.
Regardless of the reason, interruptions cause delays for the team. A one-day interruption slows down the team by more than just one day. Putting aside partially completed work and coming back to it later causes a ripple effect many times the cost of the initial delay. Stopping and starting inevitably causes unwanted extra delay.
Consequences of Interruptions
Interruptions have a lot of negative consequences.
- It pushes back work that the team had committed to which impacts other teams.
- Delivery time is pushed out.
- The team may have to work harder to meet their committed goals. Too much of this is not sustainable.
- It lowers the focus of the team.
- A pattern of interruptions leads to an unpredictable environment which lowers morale.
How to Avoid Interruptions
One way to help stop interruptions is to make visible the true cost of interruptions. As obvious as it seems to the development team, it may not be obvious to others. Most teams won’t have the courage to say no to someone who has authority over them.
Making the cost of interruptions visible may prevent many interruptions. At least, it helps to create a shared understanding of the implications of interrupting the team.
Accommodating Interruptions: Low WIP and Small Stories
Oftentimes, interruptions are driven by an urgent business need and are requested knowing full well the extra cost that is required. In this case, we want to be able to accommodate the requests. The main objective is to not interrupt our workflow while doing so.
The lean principle that helps with this is to not have too much work in process (WIP), since handling interruptions with too much WIP already in motion or with stories that are too large will cause additional work for the team if they have to put aside partially completed work.
To avoid the extra delay caused by accommodating interruptions, it is important to keep the WIP low and to use small user stories which can be completed in a short time. These help the team complete any outstanding work that needs to be completed before taking on the interruption work. And this helps avoid the delay associated with context-switching their ongoing work.
Accommodating Interruptions: Adjust Plans
To accommodate interruptions, it helps to adjust the existing plans to reflect the new reality caused by the interruption. If the team uses kanban to manage their work, no adjustment is really required; taking on the interrupting work will cause all backlog items to be delayed, but no re-planning is required. If the team uses iterations to manage their work, some already planned work for the iteration may need to be pushed back to the product backlog to make room for the new work within the team’s capacity.
Accommodating Interruptions: Make It Visible
To accommodate interruptions, it is important that the team communicates and makes visible the consequences of taking on this extra work. If the team uses kanban they can illustrate the cost with the help of delayed delivery of de-prioritized stories. If the team uses iterations to manage their work, the cost of the interruption can be illustrated with the value of stories that had to be removed from the iteration and put back on the product backlog.