The official website of TIDB introduces that TiKV’s storage engine is based on RocksDB, but TiFlash is not introduced. What is TiFlash’s storage engine based on?
Just quote from https://docs.pingcap.com/tidb/stable/tiflash-overview
TiFlash provides the columnar storage, with a layer of coprocessors efficiently implemented by ClickHouse. Similar to TiKV, TiFlash also has a Multi-Raft system, which supports replicating and distributing data in the unit of Region (see Data Storage for details).
So it’s based on a modified version of ClickHouse.