Gosh, I wish I had a good answer. Riak (and Riak-DT) were the best I knew of in this regard, but Basho folded and I haven't kept track of the level of community/corporate support available. Not sure where Riak stands these days. There are a bunch of prototype databases experimenting with CRDTs and other eventually-consistent mechanisms, but I'm not sure which ones have garnered significant traction in the industry yet.
It's extremely rewarding to read what you've written there, thank you!
It's true. The community is keeping Riak alive, and pushing it forward. The CRDT stuff has not been worked on for a long time, despite there being numerous tabled improvements in that area SINCE 2014. It was neglected by the "new" management that crashed Basho into the ground as being "complicated computer science nonsense". Since then I've been unable to do the CRDT work for Riak I wanted, due to lack of time, and no one willing to pay for it (despite numerous bait-and-switch offers for completing the bigsets work.)
The CRDT work in riak needs:
1. the smaller/more efficient map merging
2. some new types from Sam merging (range reg etc)
3. the bigsets work completing and integrating (this enables delta-CRDTs)
4. big maps (built on the above work)
When it has all that it would be at the place I'd envisioned for it, before everything went super bad at Basho. I work at Joyent now, so can't dedicate any time to taking the CRDT work forward, though I really wish I could. I still have a deep interest in the EC datatypes world.
IMO, at the time it was released (2014) Riak had ground breaking support for convergent datatypes, since then it has only lost ground. Am I bitter? Yes, a little.
WRT other systems with CRDT support, https://www.antidotedb.eu/ came out of the syncfree research project.
Chistopher Meiklejohn's work is industrial grade, state of the art, actively developed, and highly recommended. https://github.com/lasp-lang
As others have mentioned, REDIS also uses CRDTs for MDC replication, and has CRDT co-inventor Carlos Baquero on the tech board.
Riak still seems to have a decently active community; all of the formerly commercial-only features have been open sourced, and there have been multiple community releases since the demise of Basho, with another one coming out soon. I've seen a fair amount of activity on the riak-users mailing list lately too, and there is also paid support available via a couple different companies last I checked.
