A big difference is that TiDB is not ready for production yet. Having followed to the project for a while, another distinction is that TiDB is operationally mo

A big difference is that TiDB is not ready for production yet. Having followed to the project for a while, another distinction is that TiDB is operationally more complex. You need to build and deploy TiDB (high-level query engine), TiKV (key/value store) and PD ("placement driver", which coordinates sharding and data migration) separately. TiDB is stateless and can be scaled freely, but TiKV and PD are both stateful and implement their own distributed consensus systems. PD actually embeds Etcd, whereas TiKV has its own Raft implementation in Rust. Compare this to Cockroach, which has a single monolithic daemon that you deploy everywhere, which contains both the distributed query engine, the key/value store, consensus/cluster coordinator, etc. (There may be benefits or drawbacks to the difference in design; I don't know the internals of either project well enough to debate that.) For an internal project I'm working on, running TiKV standalone actually looks very interesting, but it's not very well documented yet.