Introduction to DDD, CQRS, and Event Sourcing with Axon Framework

Covers basic principles of Domain Driven Design, Command Query Responsibility Segregation and Event Sourcing.

Gives an introduction to the Axon Framework with a code example available at https://github.com/m1l4n54v1c/meetup

Transcript

1. Introduction to DDD, CQRS, and Event Sourcing with Axon Framework Milan Savić Software Engineer @ AxonIQ milan.savic@axoniq.io MilanSavic14
2. Layered Architecture
3. Everyone follows rules
5. Rich Domain Model VS Anemic Model • Contains all business rules • Requires time • Contains state & behavior • Has clear boundaries • Easier to refactor • Follows OOP • Business rules are scattered • Can be implemented quickly • Contains only state • Boundaries are not clear • Not so easy to refactor • Feels more like procedural programming
6. DDD is about mapping business domain concepts into software artifacts. Source: https://www.infoq.com/articles/ddd-in-practice
7. Bounded context
8. DDD Building Blocks •Entity •Value Object •Repository •Aggregate •Event •…
9. Command Query Responsibility Segregation • A command changes the state of an object, but does not return any data, while • a query returns data and does not change any state.
10. Just join few tables...
11. Why CQRS? • Simpler, faster queries • Scaling reads and writes separately • Choosing the correct data storage • Enabling Event Sourcing
12. Event Sourcing • Events as a single source of truth in the system • Full audit log • State is always recreated from events (snapshots) • Efficient writes • Food for ML and BigData
13. Event Sourcing - challenges • Event structure • Security • Speed
14. CQRS + ES Image source: https://sookocheff.com/post/architecture/what-is-cqrs/
16. Vision & Strategy - Originally • CQRS Framework for Java • However • CQRS is not the goal • CQRS is optional • Event Sourcing is optional • DDD is optional
17. Vision & Strategy • Framework for building evolutionary Message-Driven Microservices
18. $
19. DEMO https://github.com/m1l4n54v1c/meetup
20. Event-driven thinking in design, architecture, technology and organization with: Russ Miles, Allard Buijze, Alberto Brandolini, Mathias Verraes, Frans van Buul, and more… Register at: axoniq.io/conference
21. Zero-config location transparency & elastic scalability Application structure insight Manage (tracking) processors (including dynamic scaling) Fast & reliable storage of unbounded events streams Optimized for Event Sourcing
22. Thank you! Q&A