Author here. We've spent the past year adding read committed isolation to CockroachDB.

There were many interesting design decisions, such as:

- whether to use multiple snapshots or a single snapshot per statement

- how to handle read uncertainty intervals

- how to incorporate SELECT FOR UPDATE locking into Raft

- how to handle SELECT FOR UPDATE subqueries

- how to prevent lost update anomalies between two UPDATEs

Some of the gory details are in the public RFC: https://github.com/cockroachdb/cockroach/blob/master/docs/RF...

This blog post just discusses the last point, but please AMA.