Video and slides synchronized, mp3 and slide download available at URL http://bit.ly/1IEleaz. Dan North describes a model for thinking about the age of code and argues for replaceability as a first class concern. He also discovers that if one optimizes for both replaceability and consistency he can end up with something that looks a lot like microservices. Filmed at qconlondon.com. Dan North uses his deep technical and organisational knowledge to help CIOs, business and software teams to deliver quickly and successfully. He puts people first and finds simple, pragmatic solutions to business and technical problems, often using Lean and Agile techniques.

1. Microservices: software
that fits in your head
Dan North
@tastapod

2. InfoQ.com: News & Community Site
• 750,000 unique visitors/month
• Published in 4 languages (English, Chinese, Japanese and Brazilian
Portuguese)
• Post content from our QCon conferences
• News 15-20 / week
• Articles 3-4 / week
• Presentations (videos) 12-15 / week
• Interviews 2-3 / week
• Books 1 / month
Watch the video with slide
synchronization on InfoQ.com!
http://www.infoq.com/presentations
/microservices-replaceability-
consistency

3. Presented at QCon London
www.qconlondon.com
Purpose of QCon
- to empower software development by facilitating the spread of
knowledge and innovation
Strategy
- practitioner-driven conference designed for YOU: influencers of
change and innovation in your teams
- speakers and topics driving the evolution and innovation
- connecting and catalyzing the influencers and innovators
Highlights
- attended by more than 12,000 delegates since 2007
- held in 9 cities worldwide

4. What is the point of
software development?

5. What is the purpose of
software development?

6. business impactcreate
What is the purpose of
software development?

7. business impactcreate positive
What is the purpose of
software development?

8. What is the goal of
software development?

9. What is the goal of
software development?
to business impact
minimise lead time

10. What is the goal of
software development?
to business impact
minimise lead time
sustainably

11. The goal is not to
produce software!

12. produce

13. produce
production

14. produce
production
productive

15. ≠
effective
productive

16. Code is not the asset…

17. Code is not the asset…
Code is the cost!

18. Code is not the asset…
Code is the cost!
- writing code costs

19. Code is not the asset…
Code is the cost!
- writing code costs
- waiting for code costs

20. Code is not the asset…
Code is the cost!
- writing code costs
- waiting for code costs
- changing code costs

21. Code is not the asset…
Code is the cost!
- writing code costs
- waiting for code costs
- changing code costs
- understanding code costs

22. understanding code

23. understanding code
code I know

24. understanding code
code I know
code everyone knows

25. understanding code
code I know
code everyone knows
code no-one knows!

26. Code should be
stabilised
or
killed off

27. Code should be
stabilised
or
killed off
fast!

28. Two complementary
patterns

29. Two complementary
patterns
Short Software Half-Life

30. Two complementary
patterns
Short Software Half-Life
Fits In My Head

31. Short Software Half-Life

32. Short Software Half-Life
Design considerations

33. Short Software Half-Life
- write discrete components
Design considerations

34. Short Software Half-Life
- write discrete components
- define component boundary
Design considerations

35. Short Software Half-Life
- write discrete components
- define component boundary
- define component purpose
Design considerations

36. Short Software Half-Life
- write discrete components
- define component boundary
- define component purpose
- define component responsibility
Design considerations

37. Short Software Half-Life
Stewardship considerations

38. Short Software Half-Life
- write component tests and docs
Stewardship considerations

39. Short Software Half-Life
- write component tests and docs
- optimise for replaceability
Stewardship considerations

40. Short Software Half-Life
- write component tests and docs
- optimise for replaceability
- expect to invest in stabilising
Stewardship considerations

41. Short Software Half-Life
- write component tests and docs
- optimise for replaceability
- expect to invest in stabilising
- build a stable team
Stewardship considerations

42. Fits In My Head

43. Fits In My Head
- multiple dimensions

44. Fits In My Head
- multiple dimensions
- multiple scales

45. Fits In My Head
- multiple dimensions
- multiple scales
- “What would James do?”

46. Fits In My Head
- multiple dimensions
- multiple scales
- “What would James do?”
Contextual Consistency

47. Fits In My Head
- multiple dimensions
- multiple scales
- “What would James do?”
Contextual Consistency
- agree guiding principles

48. Fits In My Head
- multiple dimensions
- multiple scales
- “What would James do?”
Contextual Consistency
- agree guiding principles
- agree idioms

49. Fits In My Head
- multiple dimensions
- multiple scales
- “What would James do?”
Contextual Consistency
- agree guiding principles
- agree idioms
- difference is data

50. Fits In My Head
- multiple dimensions
- multiple scales
- “What would James do?”
Contextual Consistency
- agree guiding principles
- agree idioms
- difference is data
- familiarity ≠ simplicity

51. Replaceable Component
Architecture

52. Replaceable Component
Architecture
sustainably…

53. Replaceable Component
Architecture
sustainably…

54. Replaceable Component
Architecture
sustainably…

55. Replaceable Component
Architecture
sustainably…

56. Replaceable Component
Architecture
sustainably…

57. Replaceable Component
Architecture
sustainably…

58. Replaceable Component
Architecture
sustainably…
“little computers
passing messages”

59. Replaceable Component
Architecture
sustainably…
“little computers
passing messages”
— Alan Kay

60. Replaceable Component
Architecture
sustainably…
“little computers
passing messages”
— Alan Kay

61. Microservices can be a
Replaceable Component
Architecture

62. Microservices can be a
Replaceable Component
Architecture
- if you choose to optimise for
replaceability and consistency

63. Microservices can be a
Replaceable Component
Architecture
- if you choose to optimise for
replaceability and consistency
- smaller is not necessarily better

64. Microservices can be a
Replaceable Component
Architecture
- if you choose to optimise for
replaceability and consistency
- smaller is not necessarily better
- more replaceable is better

65. Kill code fearlessly!

66. Kill code fearlessly!
code I know
code everyone knows
code no-one knows!

67. Kill code fearlessly!
code I know
code everyone knows

68. Thank you!
Dan North
@tastapod
http://dannorth.net
http://leanpub.com/software-faster

69. Watch the video with slide synchronization on
InfoQ.com!
http://www.infoq.com/presentations/microservices
-replaceability-consistency