Modernizing your legacy database to Java + MongoDB Atlas doesn’t have to mean sacrificing batch performance. By leveraging bulk operations, intelligent prefetching, and parallel execution, we built an optimization framework that not only bridges the performance gap but, in many cases, surpasses legacy systems. In workloads where jobs were previously running 25–30x slower before using this framework, it brought execution times back on par and, in some cases, delivered 10–15x better performance.