TiKV is built on top of RocksDB, see our chief engineer’s speech of how we used RocksDB in TiKV: https://pingcap.com/blog/2017-09-15-rocksdbintikv/

Because of the write amplification issue of RocksDB, we build a RocksDB plugin, TiTan. Here is its design and implementation detail: https://pingcap.com/blog/titan-storage-engine-design-and-imp...