Concurrency crossroads: Choosing between reactive programming and virtual threads

This talk, presented by Willem Jan Glerum from Lunatech, delves into modern Java applications and their concurrency management, recorded at Open Community Experience 2026 in Brussels. The session compares traditional blocking I/O models with reactive programming and the newly introduced virtual threads from Project Loom. It highlights the limitations associated with blocking I/O, including thread idling during external operations, and the complexities that arise from using thread pools in cloud environments.

Glerum discusses the principles of reactive programming as a solution to these issues, portraying its event-driven model that enhances resource efficiency while complicating code structure and debugging. He then introduces virtual threads, which facilitate a lightweight concurrency model without compromising performance, and explores the concept of structured concurrency as a way to manage parallel tasks effectively, addressing concerns like thread leaks and cancellation strategies.