Describe the symptoms that led you to suspect a race condition, your debugging approach, and why your chosen solution was the right fit.
Strong answers demonstrate: understanding of shared state problems, systematic debugging approach (logging, reproducing under load), and appropriate solutions (locks, atomic operations, optimistic concurrency, queue-based processing). Best candidates discuss prevention strategies and testing for concurrency issues.
Advanced question that separates experienced developers from intermediates. Concurrency bugs are notoriously difficult. Candidates who have diagnosed and fixed one demonstrate deep systems understanding.