Episode-226-Eric-Evans-on-Domain-Driven-Design-at-10-Years

Event Sourcing

Event sourcing is a modeling technique that emphasizes storing state changes rather than the current state. Eric Evans explains that traditional systems focus on the current state, whereas event sourcing records each change, allowing the state to be derived from these changes. This approach is particularly beneficial for high-volume systems, as it allows for frequent updates without altering objects in place, thus enhancing scalability and parallelization 1.

It's really making the model more explicit about the changes.

--- Eric Evans

Marcus Blankenship inquires about the relationship between event sourcing and Domain-Driven Design (DDD), highlighting its role in event-centric problems 2.

   

CQRS

Command Query Responsibility Segregation (CQRS) is an architectural pattern that separates read and write operations to improve system efficiency. Eric Evans describes how CQRS and event sourcing emerged together, often working in tandem but remaining distinct concepts 3. In CQRS, commands handle updates, while queries manage data retrieval, allowing each to scale independently and efficiently 4.

The command part is where we have to deal with all the issues of, well, what if, you know, a command came in to cancel the order and we've already shipped it?

--- Eric Evans

This separation ensures that complex business logic is handled in the command side, while the query side remains simple and fast.