Scrum vs Kanban vs Lean vs XP: which agile method fits
Scrum is a good starting point for a team new to agile and building new features in fixed sprints. Kanban suits a team that must react quickly to changing priorities, such as one running a live service. Lean suits early discovery of user needs, and XP suits small software teams facing changing requirements and high risk.
What each method is
Scrum is the most commonly used agile method. It gives a highly structured model with clearly defined roles and responsibilities, which helps traditionally structured organisations moving to agile.
Kanban was inspired by production systems such as Toyota's that focus on reducing waste and improving quality. It is a way of visualising and improving current working practices so that work flows through the system quickly.
Lean software development is also adapted from lean manufacturing. Its principles aim to help a team focus on reducing waste, delivering quickly, learning and improving, and using evidence and data to make decisions.
Extreme Programming (XP) is a set of planning, managing, designing, coding and testing rules for small software teams of about 2 to 12 programmers working with an on-site customer.
Choosing between them
GOV.UK says Scrum is most useful when building a new product or service, enhancing existing features, or adding new features in each sprint.
Kanban helps a team find bottlenecks in its processes, control the amount of work it is doing and predict output from actual delivery. It is particularly useful when the team must react quickly to changing priorities. A team running a live service with urgent requests may find sprints constraining and move to Kanban while keeping daily stand-ups, retrospectives and regular progress reviews.
Lean lets a team focus on learning as quickly as possible, so its tools are useful when the team is first discovering its users' needs.
XP was created for domains whose requirements change and for high-risk projects. It needs automated testing and cannot be used with a huge staff.
Mixing methods
GOV.UK says a team does not have to use one method only. It can take tools and techniques from several, as long as it understands why it chose each one and its agile objective.
Where the exam catches people
Believing Kanban is the best first method for a team new to agile with a traditional structure: GOV.UK names Scrum as the good starting point because of its clear roles.
Believing moving from Scrum to Kanban means dropping stand-ups and retrospectives: GOV.UK says the team can keep them.
Believing a team must pick one method only: tools and techniques can be combined if the team knows why it uses each.
Believing XP scales to any team: it is set up for small groups and cannot be used with a huge staff.