The document discusses Command Query Responsibility Segregation (CQRS) as an architecture pattern that addresses scalability issues by separating read and write operations. It highlights the importance of considering constraints while designing systems and emphasizes that CQRS is not synonymous with event sourcing. The content includes references to a GitHub implementation and acknowledges contributions from various individuals.

1. Thomas PIERRAIN
@tpierrain
Bruno BOUCARD
@brunoboucard
Tomasz JASKULA
@tjaskula
Eric VERNIE
@EricVernie
CQRS
(without Event Sourcing)

2. Why CQRS

3. Scalability issues?

4. The Pareto
Principle
80-20
Root cause
0%0%
80%
reading
20%
writing

5. …only one central
component to deal
with a wide range
of constraints.
With…

6. Do you have those constraints in mind
while designing your architectures?
A question
(for you)

7. How to optimize an app that has to scale
for massive read accesses?
So…

8. This is where
CQRS is…

9. CQRS (short version)

10. CQRS splits the 80s and the 20s

11. CQRS splits the 80s and the 20s
20 % of time
80 % of time

12. C
Q
R
S
Behind the acronym
( powered by Greg YOUNG - @gregyoung )

13. Command
Query
Responsibility
Segregation
Behind the acronym

14. Command
Query
Responsibility
Segregation
Behind the acronym

15. CQRS illustrated

16. CQRS illustrated

17. CQRS illustrated

18. CQRS illustrated

19. CQRS illustrated

20. CQRS illustrated

21. CQRS illustrated

22. CQRS illustrated

23. CQRS illustrated

24. CQRS illustrated

25. CQRS illustrated

26. CQRS illustrated

27. CQRS illustrated

28. CQRS illustrated

29. CQRS illustrated

30. Classical
transactional
databases
RDBMS
(ACID)
« ready-to-eat
data », Caches,
non-normalized
models,
(no SQL)
CQRS illustrated

31. Command
TRIGGERS AN ACTION
Modify the state of the system
>> Don’t return data ! <<
Imperative Verb
Ex: BookARoom
Query
ASKS FOR AN INFORMATION
Read-only!
Get back data
Imperative Verb
Ex: GetAvailableRooms
Event
ALREADY HAPPENED
(Immutable)
Past-tense
Ex: RoomBooked

32. Demo

33. Open Source Implementation available on GitHub
2 main parts:
CoreClr (Runtime execution) (C++)
CoreFx (including classes, collections, file systems, xml, etc.) (C#)
ASP.NET Core 1.0 framework relies on it
Classic deployment or
Container deployment (Linux or Windows)
.NET Core
// Licensed to the .NET Foundation under one or more agreements.

38. Live coding

39. Wrap-up

40. Warning!

41. …a top-level architecture pattern
Use it for components under stress
Do not generalize its usage for all the components of your platform!
CQRS is not…

42. Event Sourcing
Also, CQRS is not…

43. CQRS Event Sourcing
but
CQRS != Event Sourcing

44. To conclude…

45. Well-separated read and write concerns
CQRS is mostly
Queries
Caches, Ready-
to-eat data
(no SQL)
Commands
Transactionnal
ACID

46. Merci aussi à Rui CARVALHO, Mendel MONTEIRO-BECKERMAN,
Olivier COANET et Clément BOUDEREAU ainsi que Greg YOUNG
pour leurs feedbacks et idées pour ce talk.

47. CQRS origins

48. Origine de CQRS

49. Origine de CQRS

50. Origine de CQRS

51. Wanna play the lab @home?
Follow the white rabbit here:
https://github.com/tpierrain/CQRS/blob/master/LabInstructions.
md

52. @microsoftfrance @Technet_France @msdev_fr
@tpierrain @brunoboucard @tjaskula @EricVernie