How do you describe a challenging project you worked on previously?

In my last role, we faced a critical latency issue in our payment processing system during peak hours. My task was to identify the bottleneck and resolve it without downtime. I analyzed the logs and discovered a database locking contention issue. I refactored the transaction logic to use optimistic locking and implemented connection pooling. I coordinated with the QA team to run stress tests. As a result, we reduced latency by 40% and eliminated timeouts, handling a 50% traffic surge smoothly. This experience taught me the importance of proactive monitoring and scalable architecture.