ScyllaDB is still the fastest at a key/value workload with per-query consistency settings and quorum reads/writes across multiple regions. If you need high-performance and low-latency, ScyllaDB wins. They are close to v3.0 which will have global secondary indexes and materialized views to improve data model flexibility. FoundationDB is also key/value but much lower-level and well proven for reliability. Don't have much experience with it and the latest release just introduced multi-regional capabilities, but the general tooling and documentation is still rough and it would take more effort to build a higher-level querying layer or client library.

TiDB is interesting, but missing more features from MySQL than CRDB is missing from PostgreSQL, so it's effective if you want sharding on mysql but will need a few more releases before it gets polished. Vitess and Citus are good options if you just want sharding on top of existing mysql or postgres with full query support within a shard. There's also Yugabyte which is multi-modal Redis/Cassandra/SQL offering with multi-regional capabilities.

CRDB is a great product with some of the easiest operations (although key management is a nightmare that they do not have a good plan for). It's fast enough for point-lookups and makes it easy to distribute and replicate your data across zones and regions. All nodes are part of a single cluster so read and write latencies will be high for global deployment, with the enterprise version having a workaround for local regional reads using pinned covering indexes. That works, but further lowers write performance.

It also has trouble with large transactions and the middle ground between OLTP and OLAP with heavy joins. Good choice if you need easy scalability and SQL interface over performance and complex queries.