Logical replication has been one of the more welcomed advancements to Postgres in recent years. Postgres 10 will feature a number of updates to it. Get a primer of what it is, and why you would use it.
Postgres-BDR is a multi-master replication system for geographically distributed clusters using highly efficient, asynchronous logical replication. It supports anything from 2 to more than 48 nodes in a distributed database.