This paper presents a transactional framework for low-latency, high-performance, concurrent event processing in Java. At the heart of our framework lies Reﬂexes, a restricted programming model for highly responsive systems. A Reﬂex task is an event processor that can run at a higher priority and preempt any other Java thread, including the garbage collector. It runs in an obstruction-free manner with time-oblivious code. We extend Reﬂexes with a publish/subscribe communication system, it- self based on an optimistic transactional event processing scheme, that provides eﬃcient coordination between time-critical, low-latency tasks.We report on the comparison with a commercial JVM, and show that it is possible for tasks to achieve 50 µs response times with way less than 1% of the executions failing to meet their deadlines.