RECODS: Replica consistency-on-demand store

Replication is critical to the scalability, availability and reliability of large-scale systems. The trade-off of replica consistency vs. response latency has been widely understood for large-scale stores with replication. The weak consistency guaranteed by existing large-scale stores complicates application development, while the strong consistency hurts application performance. It is desirable that the best consistency be guaranteed for a tolerable response latency, but none of existing large-scale stores supports maximized replica consistency within a given latency constraint. In this demonstration, we showcase RECODS (REplica Consistency-On-Demand Store), a NoSQL store implementation that can finely control the trade-off on an operation basis and thus facilitate application development with on-demand replica consistency. With RECODS, developers can specify the tolerable latency for each read/write operation. Within the specified latency constraint, a response will be returned and the replica consistency be maximized. RECODS implementation is based on Cassandra, an open source NoSQL store, but with a different operation execution process, replication process and in-memory storage hierarchy.