Does Neki solve for this, and if so how? My understanding of CAP theorem is that this basically requires some compromises around availability, but I'm curious as to what that looks like in practice here.
The usual way to run it is that you partition your db based on something like a user, so that single user gets a consistent DB, but anything cross-shard may not be.
I know when I worked at Block, Cashapp was using Vitess and getting cross-shard DB writes down and functioning correctly was one of the major blockers to adoption. (though I just did tls management for vitess and didn't write any workloads on top of it, so my impression might be a bit off)
If you have serializable on each shard and you chop transactions so you have no cross shard transactions, the application is technically still serializable, it just behaves like two independent deployments of the application for different shards