In 2015, MySQL Cluster (NDB Cluster engine) benchmarked 200m transactions/second on commodity hardware [ref]. It was read-committed transactions, not snapshot isolation, but still impressive. NDB has now become RonDB, but is still based on a non-blocking 2-phase commit protocol and is GPL-v2.

RonDB now has support for infiniband, so ought to blow through the 1B ops/sec. For reference, that is 1 GHz of transactions/sec.

[ref] https://www.slideshare.net/frazerClement/200-million-qps-on-...