Concurrent objects with asynchronous messaging are an increasingly popular way to structure highly available, high performance, large-scale software systems. To ensure data-consistency and support synchronization between objects such systems often use an atomic commitment protocol such as Two-Phase commit (2PC). In highly available, high-throughput systems, such as large banking infrastructure, however, 2PC becomes a bottleneck when objects are highly congested (one object queuing a lot of

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... ges at the same time because of locking). In this paper we introduce Path-Sensitive Atomic Commit (PSAC) to address this situation. We start from message handlers (or methods), which are decorated with pre- and postconditions, describing their guards and effect. This allows the PSAC lock mechanism to check whether the effect of two incoming messages at the same time are independent, and to avoid locking if this is the case. As a result, more messages are directly accepted or rejected, and higher overall throughput is obtained. We have implemented PSAC for a state machine-based DSL called Rebel, on top of a runtime based on the Akka actor framework. Our performance evaluation shows that PSAC exhibits the same scalability and latency characteristics as standard 2PC, but obtains up to 1.8 times median higher throughput in congested scenarios.