A project manager is working on a user story about migrating to a new version...

A spike is a time-boxed research activity used in Agile to explore uncertainties or unknowns, such as dependencies in this case. If the product owner is unsure about the risks related to migrating to a new version of a database, they can request a spike from the team. This will allow the team to investigate the dependencies, assess potential risks, and gather the necessary information to move forward with the user story. This helps reduce uncertainty and makes it easier to make informed decisions about the next steps.