From last year, my team study and start to apply microservices architecture to our company projects. And beside of benefits of that architecture, we also started to face with many bad-part of it (cost and benefit :D). One of the biggest problems is a separation of data on many services and raise the hard-way to get the big picture of information for client view. And, applying CQRS (Command Query Responsibility Segregation) and ES (Event Sourcing) to projects architecture is the best choice to resolve that issue. Let's discuss very powerful patterns and how to apply them in our projects.

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!