Apply Decisions at the Last Possible Moment

According to Agile principles, having people with the right skills and expertise is critical in producing high quality work. The best option in this case would be to hold off on the decision until the new member with much-needed expertise joins the team. This will help ensure that the decision made is the most appropriate and well-rooted in expertise. Starting development tomorrow regardless of the new joiner could lead to the team developing a feature that does not fully utilize the expertise of the new team member. Asking the current team to upskill and start development immediately might rush the process and lead to gaps in knowledge and understanding. Cancelling the development until further notice would not be a productive way forward.

The process of Agile project management is iterative and necessarily flexible, meaning that changes can, and often should, be considered during the course of the project. However, a thorough evaluation of the change suggested is crucial before accepting it, as it can potentially impact other aspects of the project. Accepting the change request immediately or rejecting it immediately is not a good approach because both deprive you of the chance to assess the ramifications and benefits the change may bring. Also, the statement that 'no changes are accepted in Agile projects' is incorrect as Agile approach is all about being flexible and adapting to changes when needed. Therefore, the best course of action is to 'Defer the decision and evaluate this change in the product backlog refinement session.'

The best course of action in this Agile environment would be to place the component in the backlog and then decide on its inclusion in the sprint when more information is available. In Agile methodologies, it is common to deal with unexpected complexities by reassessing and reprioritizing the project backlog. This approach provides more flexibility for the team to manage and mitigate risks effectively. On the contrary, forcing the team to deliver the complex component within the next sprint (as suggested in another answer) could lead to poor quality or even failure due to the underestimated complexity. Excluding the component entirely from the project is also a wrong approach as it doesn't address the problem but merely avoids it. Finally, escalating the decision to senior management contradicts one of the Agile principles: that the most efficient and effective method of conveying information to and within a development team is face-to-face conversation. Therefore, the decision about the component should ideally be made by the people who are most familiar with the project, namely the development team.