The document discusses three choices for dealing with complex problems in software architecture: 1. Using an ORM can lead to confused domain models 2. Using a "fancy database" like a graph or search database can lead to the wrong data models 3. Storing data in simple tables can result in data loss It then presents event sourcing as an alternative approach that avoids these issues by having an event store that appends immutable events, and generates views of current state from replaying the events. This allows for scaling, minimal code, and avoiding data loss or complex models.

1. hello!
@pieterkoornhof
sneakycode.net

2. Assume Complex
Problems

3. accidental
complexity

4. 3 Choices

5. #1

6. sql
#1
orm
logic

7. sql
#1
orm
logic
dto
+
service
ddd
entities

8. sql
#1
orm
logic

9. sql
#1
orm
logic
views

10. sql
#1
views

11. sql
#1

12. #1 Confused Models

13. #2

14. Full Text
Searching
Related
Items
Data
Blobs
Reporting
Fancy
Database
#2

15. Graph
Relational
Fancy
Database
#2
Search
Index
Document

16. App
#2
Graph
Relational
Search
Index
Document

17. #2 Wrong Models
( Sucky Database )

18. #3

19. #3
Cart
Product
Customer
*

20. Peets Cart
#3

21. ++++
++++ + -
Peets Cart
#3

22. Cart
Product
Customer
*
1. Added Apple
2. Added Apple
3. Added Rocket
4. Added Camera
5. Removed Rocket
6. Added Bike
7. Paid
#3

23. Cart
Product
Customer
*
Removed
Item
*
#3

24. 1. Added Apple
2. Added Apple
3. Added Rocket
4. Added Camera
5. Removed Rocket
6. Added Bike
7. Paid
Cart
Product
Customer
*
Removed
Item
*
#3

25. #3 Data Loss

26. #1 Confused Models #2 Wrong Models #3 Data Loss
accidental complexity

27. data Graph
Relational
Fancy
Database
Search
Index
Document
#1 Confused Models #2 Wrong Models #3 Data Loss
1. Added Apple
2. Added Apple
3. Added Rocket
4. Added Camera
5. Removed Rocket
6. Added Bike
7. Paid
CQRS Polyglot Data Event Sourcing

28. Event Sourcing

29. event store
Stores Events
removedFromCart {
cartId: 2134-DSF3-SDFW,
item : Rocket,
quanity: 1
}
1. Added Apple
2. Added Apple
3. Added Rocket
4. Added Camera
5. Removed Rocket
6. Added Bike
7. Paid

30. event store
Append Only
Immutable
No Updates No Deletes

31. I want
to Pay

32. Command
(write)
App
pay {
cartId: 2134-DSF3-SDFW,
discount: 31%,
cardDetails: Visa
}

33. Command
(write)
App
event
store f(events) => state
f(state, command) => event(s)
1. Added Apple
2. Added Apple
3. Added Rocket
4. Added Camera
5. Removed Rocket
6. Added Bike
7, Paid
Cart
Product
Customer
*

34. Command
(write) read
App
event
store
sql
neo4j
f(events) => viewState

35. command eventLogic View

36. command eventLogic View
store
Just Messages
No Data
Loss!

37. command eventLogic View
Things Happend
Replay!

38. command eventLogic View
Scale!

39. command eventLogic View
app.Handle( Command )
store.Load<T>( Id ) store.Save( T )
Minimal Boilerplate!

40. command eventLogic View
input
output
Testing!
events, command => event(s)

41. command eventLogic View
jake
sas
Workload!
rob

42. Characteristics
Multiple Databases
Operational Complexity
Eventual Consistency

43. 3 Choices

44. geteventstore.com

45. github.com/SneakyPeet/EasyEventSourcing

46. thanx!
@pieterkoornhof
sneakycode.net

47. Credits
Special thanks to all the people who made and released
these awesome resources for free:
✘ Presentation template by SlidesCarnival
✘ Photographs by Unsplash