Start here. This is the direct spoken answer to practice first.
Why this question matters
Estimates are often wrong. The interview signal is whether the candidate notices early, communicates clearly, and adjusts responsibly.
Use this as an adaptable model, not a story to claim as your own. Replace the project, constraints, your actions, collaborators, outcome, evidence, and reflection with truthful details from your experience.
I underestimated a partner integration because I treated it mainly as field mapping. The real work included network access, inconsistent sandbox behavior, retry rules, and reconciliation after uncertain responses. Once that became clear, I documented the new scope and the remaining unknowns and raised it before the original deadline. I reset expectations with the lead and product owner instead of hiding the uncertainty inside one large task.