Event Sourcing is supposed to be a great thing: silver bullet; at least. But only if your business case requires it. And if you event-source, you of course need CQRS. Unless you don't. After all, if it's business critical, you really want to use DDD. Enough of the theory? How about some practical introduction to the world of commands, aggregates, events, projectors and process managers? After this session you'll surely have a better idea of what all of this is about. https://www.youtube.com/watch?v=cUXi9fUqWQ0

1. A practical introduction
to Event Sourcing
and Command Query
Responsibility
Segregation

2. Robert Lemke
CEO Flownative
Project Founder Neos
robert@flownative.com
@robertlemke

3. CRUD
Create, Read, Update, Delete

4. CQRS
Command Query
Responsibility Segragation

5. Event Sourcing
Store all changes to the system,
rather than it’s current state.

6. Event Sourcing
Store all changes to the system,
rather than it’s current state.

7. Mathias Verraes (http://verraes.net)

8. Motivation for Event Sourcing

9. Expressivity

10. Distributed /
event-driven architecture

11. Audit log*

12. Debugging

13. New representations / analysis

14. Easy storage

15. Commands

16. Do that! (imperative)

17. Command Handlers
will handle commands.
They don’t return a
result, only accept or
reject commands.

18. $commandHandler-
>handle($command);

19. Events

20. Domain Events:
something interesting
in the domain /
business

21. (infrastructure)
events: user clicked
button, log has been
rotated, file upload
failed

22. Events are something
which happened in the
past

23. You can’t change the
past, so events are
immutable

25. Event Sourcing does not
need a framework.
But Neos.EventSourcing
helps you implementing
Event Sourcing with Flow.

28. The sample domain

29. addBookToAssortment
addBookToCatalog
addBookToListOfProductsPeopleCanBuy ;-)

30. Live Demo 😱

31. Some special cases

32. Deleting a book

33. Media / assets /
binary data

34. Flow accounts, …

35. Versioning events

36. Should you try it?

37. robert@flownative.com
www.flownative.com
@robertlemke
your thoughts?