A user says they cannot see a specific Opportunity record that a colleague can see. How do you troubleshoot it?

First I confirm object access: does the user's profile or permission sets grant Read on Opportunity? Then I check record-level access, starting with the org-wide default and working through the role hierarchy, sharing rules, teams, manual shares and implicit sharing. The Sharing button or the Sharing Hierarchy on the record shows who has access and why.

I would also compare the two users with the Login As feature, if permitted, and check whether a list view or report filter is simply hiding the record rather than a true access problem.

The interviewer is looking for a structured approach: object permissions first, then record access layers, then field-level issues. Good candidates name the tools for checking access. A pitfall is jumping straight to granting View All or Modify All instead of finding the root cause.