The Rock Crusher is a tool to help us visualize a roadmap of known rocks that might flow through a backlog. However, some of the team’s work may not be planned and roadmapped rocks. We must supplement the Rock Crusher to account for this unplanned work.
Whether a rock is on our roadmap or not, it flows through the team’s Rock Crusher funnel. The backlog owner cannot escape accountability for prioritizing all the rocks in the backlog—not just the roadmapped rocks. We have developed a strategy matrix for classifying and coping with rocks using two parameters, expected and planned.
- Expected rocks are probable work—the team knows the rock is coming but may not be certain of when it will arrive. In contrast, Unexpected rocks have a low probability of occurring; literally, the team does not expect them to happen.
- Planned rocks are known either because they’re on the roadmap—explicitly planned—or because historical patterns have taught the team to plan for that work. Unplanned rocks are not on a roadmap and are not part of the team’s historical patterns. Unplanned rocks cannot be deferred, for example, planned for a subsequent sprint, and therefore have the potential to disrupt flow.
| Expected | Unexpected | |
| Planned | This classic roadmapped Rock Crusher work. Planned and expected is work that we can schedule | Although the team does not expect this Rock – there is a low probability it will be needed, the team needs to plan for it. This is the domain of Risk Mitigation. |
| Unplanned | Based on historical patterns, the team regularly receives these rocks are managed using capacity allocation. The rocks are not on the roadmap but the team anticipates them. | This is typically a crisis or black swan event. The team’s only recourse for dealing with this rock is to break the thin pipe, abandon their commitment, deal with the event, and then retrospect to understand what happened. |