Revisiting Concurrency in High-Performance NoSQL Databases.

We measure the performance of five popular databases and show that single-node performance does not scale while hosting data on high-performance storage systems (e.g., Flash-based SSDs). We then analyze each system, unveiling techniques each system uses to increase concurrent performance; our taxonomy places said approaches into six different categories (thread architecture, batching, granularity, partitioning, scheduling and low-level efficiency) and thus points towards possible remedies that can scale the system. Finally, we introduce Xyza, a modified version of MongoDB that uses a wide range of classic and novel techniques to improve performance under concurrent, write-heavy workloads. Empirical analysis reveals that Xyza is 2× to 3× faster than MongoDB and scales well (up to 32 processing cores).