Each application developer desires to provide its users with consistent results and an always-available system despite failures. Boldly, the CALM theorem disagrees. It states that it is hard to design a system that is both consistent and available under network partitions; select at most two out of these three properties. One possible solution is to design coordination-free monotonic applications. However, a majority of real-world applications require coordination. We resolve this dilemma by conjecturing that partial progress is possible under network partitions. This partial progress ensures the system appears responsive to a subset of clients and achieves non-zero throughput during failures. To this extent, we present the design of our CASSANDRA consensus protocol that allows partitioned replicas to order client requests.

翻译：每个应用程序开发者都希望为其用户提供一致的结果和始终可用的系统，即使发生故障。CALM定理却大胆地提出了不同观点。该定理指出，在网络分区情况下，很难设计出既保持一致性又具备可用性的系统；至多只能从这三个特性中选择两个。一种可能的解决方案是设计无需协调的单调应用程序。然而，大多数现实世界的应用程序都需要协调机制。我们通过提出以下猜想来解决这一困境：在网络分区下部分进展是可能实现的。这种部分进展能确保系统对部分客户端保持响应性，并在故障期间实现非零吞吐量。为此，我们提出了CASSANDRA共识协议的设计方案，该协议允许分区副本对客户端请求进行排序。