Hands-On Reactive Programming in Spring 5

Messaging system as a data store

Building on the idea of event sourcing, we may conclude that a message broker with persistence storage for messages may diminish the need for a dedicated database for individual microservices. Indeed, if all entity update events (including entity snapshots) are stored in the message broker for a sufficient period of time and can be re-read at any moment, the entire state of the system may be defined only by that event. During startup, each service may read recent event history (up to the last snapshot) and recalculate an entity's state in memory. So, a service may function by merely processing new update commands and read queries, and generating and sending entity snapshots to the broker from time to time ...