Scrum Team Composition

Scrum Team composition is very important for the success of the project. I have experienced it at many occasions. Many times, when an organization wants to take up a new important project, they tend to form an all star team - a team composed of all senior and experienced developers. Such a team composition poses following risks:

1. Senior developers are more opinionated than junior developers. Thus imagine a team of 5 people, all stars, discussing a design. Everybody will have different opinions. Many times the design choice is not clear, it's philosophical. Such heated design discussions can cause a rift amongst team members.
2. If junior developers don't work with senior developers, you loose a chance of training your junior developers.

An ideal team size is around 5 to 7. If you have a complex project that requires a much bigger team, then the project can be split into multiple scrum teams. Bigger teams tend to have multiple internal groups (with different school of thoughts) and hence struggle to arrive at a decision.

The teams should be cross functional. It should have all the skills that are necessary to complete end to end stories - front end, back end, database, testing etc. The exact mix of these skills depends upon the requirements of the project. It is possible to change the team composition every sprint if necessary. But the changes should be minimal because changing the core team every sprint will impair the desired velocity.

Scrum provides a platform for open communication and collective decision making. Open communication will immediately bring the philosophical difference of opinion to the forefront. The scrum master in most cases should not intervene design / coding philosophies battles. But if it starts going out of hand and affects productivity, it is important that the scrum master talks to them and brings everybody on the same page.