Introducing the Rock Crusher: A Flow-Based Model of Backlog Management

Figure 1.10: The Rock Crusher as Model for Backlog Management

The Rock Crusher is not yet another methodology. It is an integration of common success patterns we have observed numerous teams employ to enhance visualization and effectively manage their work in the context of "getting stories ready." Certain organizations even refer to their processes as "rock crushing." By utilizing these patterns, we gain the ability to visualize and manage all the value-adding steps within our value stream beyond just the coding steps.

The key elements of the Rock Crusher are:

• Rock: Just a cute name for backlog items. A Rock may be a user story, a feature, an epic, a capability, a use case, a defect, an initiative, or whatever local name the team is using for backlog items.
• Funnel: The turbulent flow of Rocks is throttled and stabilized in the funnel. The Rock Crusher funnel shifts our mental model of the backlog from a passive reservoir to an active learning and discovery process that results in a stabilized and throttled flow:
  • Stabilized because the backlog is prioritized through forced ranking, with few or no changes taking place in the ranking.
  • Throttled because the flow does not exceed the team’s capacity, represented by the Thin Pipe.
• Thin Pipe: A metaphor for the limited capacity of the team. The Thin Pipe can easily clog and create delays if the flow of ready Rocks is not smooth.
• Waste Gate: A critical part of the flow equation: What goes in must come out. In an agile world, not all work entering the backlog will or should be done. The Waste Gate represents our policies for explicitly removing work from the backlog.
• The Village: It takes a village of collaborating roles to stabilize and throttle the flow through the backlog.

The Product Owner Can’t Do It All: It Takes a Village

Analyst: The analyst is responsible for transforming the wants, hopes, interests, and aspirations of the customer, stakeholder, and solution owner, as well as the contributions of the subject matter expert, into a shared, clear understanding of precisely what to build. The analyst is responsible for progressively creating a better understanding of precisely what to build: the Solution.

Team: Team members are responsible for collaborating with all roles for deciding precisely what to build and are accountable for delivering on their commitments to the backlog owner.

Supporting Roles

Customer: The customer is the receiver or beneficiary of the Solution. They may be consulted or informed about decisions on precisely what to build.

Stakeholder: A stakeholder is any individual who, at a minimum, must be consulted about precisely what is being built and may also have decision-making authority in deciding precisely what to build. A customer may also be a stakeholder if they need to be consulted about decisions on precisely what to build.

Subject matter expert (SME): A SME is someone who has deep knowledge of the relevant problem domain and/or relevant technology and development practices. SMEs use their knowledge to advise other roles on deciding precisely what to build. They are responsible for providing the expertise other roles may need to perform their jobs.

The number of individuals required to perform these roles greatly depends on the size and context of the organization and the development environment.  

Summary

Let’s review some of the elements of the Rock Crusher:

• The Rock Crusher is a flow-based model of backlog management that mitigates the deficiencies of the traditional “stacked plates” model of the product backlog.
• The Rock Crusher better captures and visualizes the ambiguity that should be inherent in a backlog.
• The Thin Pipe is a metaphor for the limited capacity of the team to deliver Solution Increments. The effectiveness of the Thin Pipe relies on a steady flow of Ready backlog items.
• Rock Crusher flow is turbulent. Its purpose is to make the processes and work involved in easing that flow visible and manageable.
• The Rock Crusher model acknowledges the difficulty of the product owner role and breaks it out into a village of roles—backlog owner, solution owner, analyst, subject matter expert, stakeholder, and customer.
• A Rock is just a fancy metaphor for a backlog item. A well-formed Rock will have an intent and result in a testable, verifiable model.
• The Waste Gate is an important part of the model and explicitly demonstrates that not all Rocks in the backlog will be pulled through the Thin Pipe.
• The Rock Crusher flow equation is simply: what goes in must come out. Rocks are either pulled through the Thin Pipe or ejected through the Waste Gate.

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References

1. Brooks, Frederick P. "No Silver Bullet Essence and Accidents of Software Engineering." Computer 20(4): 10–19, 1987.

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