The document discusses Command Query Responsibility Segregation (CQRS) and event sourcing patterns, highlighting the challenges of database normalization and data retrieval in microservices architecture. It emphasizes the importance of separating models for commands and queries and provides insights into applying these concepts using frameworks like Axon, Lagom, and Eventuate. It concludes with an example application of CQRS for better understanding and implementation.

1. About CQRS & ES
Something about CQRS & Event Sourcing patterns
By trinhthethanh25390@gmail.com

2. - Problems
- Introduction to CQRS & Event Sourcing
- Apply the concepts
- Using Axon framework to implement an example
Outline

3. Problems - from a common search
215.000.000 results!!!

4. - Normalize database is hard, retrieving data from that is harder
Problems - from a common search
Which one is better?

5. - One of the principles of microservices is that a service should not directly
access another service's data store
Problems - to microservices architecture

7. Question: microservices multiple database challengers??

8. “CQRS is not a silver bullet...CQRS is not Event Sourcing...CQRS is not a good wife
...but...CQRS can open many doors”
CQRS
Greg Young

9. - Command Query Responsibility Segregation
- Separate the application into different models for Commands and Queries
CQRS - the concepts

10. - Command Query Responsibility Segregation
- Separate the application into different models for Commands and Queries
CQRS - the concepts
I want something done
Commands

11. - Command Query Responsibility Segregation
- Separate the application into different models for Commands and Queries
CQRS - the concepts
I want something done
Commands
I want to know something
Queries

12. - Command Query Responsibility Segregation
- Separate the application into different models for Commands and Queries
CQRS - the concepts
I want something done
Commands
I want to know something
Queries
UI

13. - Command Query Responsibility Segregation
- Separate the application into different models for Commands and Queries
- Event sourcing: what actually happened?
CQRS - the concepts
I want something done
Commands
I want to know something
Queries
UI
events

14. - Command Query Responsibility Segregation
- Separate the application into different models for Commands and Queries
- Event sourcing: what actually happened?
CQRS - the concepts
I want something done
Commands
I want to know something
Queries
UI
events
Event
store

15. CQRS - the flow
Image source:microsoft

16. CQRS - the components
Image source:geekabyte.io

17. Applying CQRS concept

18. - Use separate write/read model inside an application
Applying CQRS concept

19. - Use separate write/read model inside an application
Applying CQRS concept
- DB View (not bad)
- Spring JPA native query
@Query,
@NamedNativeQueries
- NoSQL/full text search store
for read side

20. - CQRS/ES based frameworks
- Axon framework
- Lagom framwork
- Eventuate ES
- ….
Applying CQRS concept

21. Example
https://github.com/3t-dev/cqrs-order-portfolio

22. Thank you!