Ensure things fail if multiple things say they own the same resource.

[big-andy-coates]

The concept of resource ownership is a powerful one. But for it to work, things need to complain if multiple things say they own the same resource, e.g. a Kafka topic.

If two services say they own a topic - that's bad, only one can.
If two aggregates say they own a topic - that's also bad.

More of a grey area is when a service, and its parent aggregate say they own a topic, which is currently normal practice. More thought needed on that...