We have spent a lot of time discussing HOW to send and receive messages. But what about the CONTENT of those messages? On the one hand, this is a fairly simple topic: you simply add whatever message body you want. On the other hand, deciding what to include and what not to include in your messages gets to the heart of some pretty important distributed system design questions. In addition, in this video I get to talk about what I think of as one of the most important techniques for building robust microservices: using Correlation IDs.