An important difference between CockroachDB and TiDB is that the former has an embedded key-value store; everything runs in the same process. TiDB is split int

An important difference between CockroachDB and TiDB is that the former has an embedded key-value store; everything runs in the same process. TiDB is split into multiple parts: TiDB proper (stateless SQL/query plan layer), TiKV (the key-value store), and PD (placement driver, the main control plane and metadata layer). TiKV also isn't a pure key-value store, as it handles some particular query operations that can be "pushed down" from TiDB to reduce network round trips. FoundationDB's role similar to TiKV. It's a pure key-value store with replication built in.