Regarding distributed(-ish) Postgres, does anyone know if something like My/MariaSQL's multi-master Galera† is around for Pg:

> MariaDB Galera Cluster provides a synchronous replication system that uses an approach often called eager replication. In this model, nodes in a cluster synchronize with all other nodes by applying replicated updates as a single transaction. This means that when a transaction COMMITs, all nodes in the cluster have the same value. This process is accomplished using write-set replication through a group communication framework.

* https://mariadb.com/docs/galera-cluster/galera-architecture/...

This isn't necessarily about being "web scale", but having a first-party, fairly-automated replication solution would make HA easier for a number internal-only stuff much simpler.

† Yes, I am aware: https://aphyr.com/posts/327-jepsen-mariadb-galera-cluster

Citus, sort of Cockroach

For HA, Patroni, stolon, CNPG

Multimaster doesn't necessarily buy you availability. Usually it trades performance and potentially uptime for data integrity.