During backlog refinement meeting, the new developer on the team asks the product owner to discuss a new performance threshold requirement and how it impacts the stories in the backlog. What should the team do?

The team has encountered a new, non-functional requirement (performance threshold) with an unknown impact on the existing backlog. The correct agile practice for handling such uncertainty is to create a spike. A spike is a time-boxed research activity or experiment that allows the team to explore the requirement, understand its technical implications, and gather enough information to estimate the effort needed to implement it. This reduces risk and enables informed decision-making before altering existing stories or committing to a specific design.

A. Adding acceptance criteria is premature. The team cannot define accurate criteria before understanding the requirement's impact through analysis.
C. A design session may be part of the work done during the spike, but creating the spike is the first step to formally allocate time for this investigation.
D. The team cannot identify specific implementation tasks before they have analyzed the requirement and its impact, which is the purpose of the spike.

1. Project Management Institute. (2017). Agile Practice Guide. Glossary, p. 153. Defines a spike as "A short, time-boxed investigation of a technique, component, or risk." Also mentioned in Section 5.2.6, p. 60.

2. Cohn, M. (2009). Succeeding with Agile: Software Development Using Scrum. Chapter 13, "The Product Backlog," describes using spikes to gain the knowledge necessary to split or estimate other stories.

3. Wake, W. C. (2002). Extreme Programming Explored. Chapter 10, "Spike," explains that a spike is a simple program created to explore a potential solution or answer a technical question.