Chapter 16

1. The message queue gets a message and has a single subscriber dequeue it. If nothing dequeues a message, it stays in the queue indefinitely (FIFO model). The Pub-Sub model gets a message and sends it to zero or more subscribers.
2. Event sourcing is the process of chronologically accumulating events that happened in a system instead of persisting the current state of an entity. It allows you to recreate the state of the application by replaying those events.
3. Yes, you can mix Gateway patterns (or sub-patterns).
4. No, you can deploy micro-applications (microservices) on-premises if you want to. Moreover, in Chapter 14, Mediator and CQRS Design Patterns, we saw that we can use CQRS even inside a single application.