[simon2Q]

Postgres-BDR works very well for its intended business use case, which is geographically distributed multiple master database. Master-slave replication is not comparable cos there is only one master. You should use as few masters as your business case requires, so it is possible you don't need BDR at all. The underlying technology is roughly the same between master-slave and master-master, so that is not a big distinction and not the key point.

Postgres-BDR is designed to solve a common problem: access to a database from users all around the world. In cases where you have a single master and multiple standbys then all write transactions must be routed globally to the same location, adding 100s of milliseconds latency and in many cases making applications unusable.

Postgres-BDR offers the opportunity to make those writes to multiple copies of the database in different locations, significantly reducing the latency for users.

What BDR doesn't solve is what you do if all your users want to update the same data at the same time. But that type of application is just not scalable. If you run such an application on any database that gives you perfect consistency and lots of other shiny buzzwords, all you get is a really, really slow application, just like you had in the first place. But it will tick all the keywords.

All distributed systems require you to understand the business case and the trade-offs required to make it work. This is not fancy technology to use because you think its cool, its for use where it is useful and important to do so. BDR gives you the tools to know whether your application will work in a distributed manner and to keep it working in production without fear.