Their paper (https://www.usenix.org/system/files/atc20-conway.pdf) reports a 6-10x speedup on insertions and 2x lower write amplification as compared to RocksDB, on fast NVMe hardware, for certain benchmarks. The authors found that RocksDB (and other storage engines) start being bottlenecked by CPU and have come up with some ways of tackling those bottlenecks, including a novel data structure named STB-tree. The current SplinterDB version has a list of acknowledged significant limitations and is not recommended for production use by the authors (yet).