Give a range, not a single number: "I estimate 3 to 5 days, depending on the API integration complexity." Then update early if it trends toward the high end.
Best answers break work into smaller tasks, account for unknowns with a range rather than a single number, use past experience as a reference, and communicate early when estimates slip. Strong candidates distinguish between estimates and commitments, and flag risks proactively rather than missing deadlines silently.
Practical skill that affects team trust. Developers who consistently under-estimate without learning are a planning risk. Those who communicate early and honestly about delays are trusted teammates. Ask: "What makes you less confident in an estimate?"