The lead developer informed the team that they have learned of some possible integration challenges...

Conduct an architectural spike immediately to decide how the functionality will be determined.

Work with the product owner to avoid the risk by determining if their requirements could be met with reporting or a similar functionality.

Continue the priority defined by the product owner on the backlog for the functionality they determined to be the highest priority.

Identify this as a risk, decide on the response, and prioritize spike to determine the solution on the product backlog.