I don't think it's true that distributed and decentralized mean the same thing. A hub and spoke rail system is centralized, but it's still a distributed system, if it has multiple trains running concurrently.* A distributed system has to coordinate somehow, and a single central DB is one way of doing it.

*: edit, maybe a better example here is a rail system with a single central dispatcher is centralized but may still be distributed

> Is it really a distributed system or just a bunch of services with a central database?

I've asked myself this question every single time I've had to use Zookeeper.

Apache Kafka being the poster child of the problem, with HBase in a close second.