I'm building an e-commerce application with PostgreSQL and Node.js, and during peak traffic, I'm frequently encountering deadlock errors when multiple customers try to purchase the same item. How can I efficiently prevent or handle these deadlocks without compromising performance?

My application uses a microservices architecture where the order service updates inventory levels in a PostgreSQL database. I've already tried setting transaction isolation levels to REPEATABLE READ and implemented basic retry logic with exponential backoff, but deadlocks still occur, leading to failed transactions and poor user experience. I'm looking for practical strategies that balance consistency and performance.