In my previous role, I worked on a backend system where we used Java to build a microservices architecture for a financial application. One of the key challenges was ensuring the system could handle high transaction volumes efficiently. To address this, I implemented asynchronous processing using Java's CompletableFuture, which allowed us to handle multiple requests concurrently without blocking threads. Additionally, I utilized caching mechanisms with tools like Redis to reduce database load and improve response times. For reliability, I incorporated circuit breaker patterns using Hystrix to gracefully handle failures and prevent cascading issues. Regular performance testing and profiling helped us identify bottlenecks and optimize code, ensuring the system remained robust and responsive under load.