Set Based Design

Each morning newspapers hit the newstands without fail. Live broadcasts are the same. Come show time they hit the air without fail. You can probably think of more examples of deadlines that are constantly achieved. So why does software development accept missed deadlines? Software development not only encourages software to be late, it has become accepted or just another risk to the project by default.


Implementing Lean Software Development introduces the concept of Set Based Design (SBD). SBD provides an answer on how to never miss a deadline every again, providing the deadline is feasible. SBD will allow software to constantly hit deadlines just as newspapers and TV shows do.

SBD requires multiple teams to implement the same functionality split over several sets (versions) of work. Each team works independently and in parallel to fulfil the same goal. This is in stark contrast to normal proceedings where each team is usually assigned to separate projects. At the end of the deadline the set that is best fit for purpose is chosen. This ensures the teams as a collective have delivered the best possible solution within the deadline. Each set should increase in scope and complexity. This means each additional set has a higher chance of missing the deadline.


The number of sets you decide upon is based on each variation, so there is no fixed limit. Assume three for the following introduction.

Set One
Set Two
Set Three


Is this waste?

No. The goal is to hit the deadline with the best possible solution. While a number of sets will never be released, the teams have hit their target. Teams should judge success on goal completion, not lines of code into production.

What are the downsides?

Trying to explain SBD and actually convincing the business to have a number of teams all working on the same project would sadly be an incredible challenge in most organisations.

When would you not use SBD?

SBD makes sense when there is a fixed scope deadline that cannot be missed. If this is not the case, iteration or refactoring at each step would suffice.


Producing an architecture that allows replacement or changes easily is another alternative, though this has risks of its own. Changeable architecture will be covered in a future post.