The “monoliths vs microservices” debate often focuses on technological aspects, ignoring strategy and team dynamics. Instead of technology, smart-thinking organizations are beginning with team cognitive load as the guiding principle for modern software. In this talk we explain how and why, based on material from the book Team Topologies by Matthew Skelton and Manuel Pais.

1. TeamTopologies.com
@TeamTopologies
Forget ‘Monoliths vs Microservices’: focus on
Team Cognitive Load
Matthew Skelton & Manuel Pais
Authors of Team Topologies
@matthewpskelton @manupaisable
ABSA - 10 February 2020

2. 2
Monoliths vs Microservices
Team Cognitive Load
Case Studies
Getting started

3. Team Topologies
3
Organizing business and
technology teams for fast flow
Matthew Skelton & Manuel Pais
IT Revolution Press
Order via stores worldwide: teamtopologies.com/book

4. Monoliths vs
Microservices
4

5. 5

6. “Start with monolith and
extract microservices.”
- Tammer Saleh
6
https://www.infoq.com/presentations/cloud-anti-patterns

7. “Don’t start with a
monolith when your goal is
a microservices
architecture”
- Stefan Tilkov
7
http://martinfowler.com/articles/dont-start-monolith.html

8. “If you can't build a
monolith, what makes you
think microservices are
the answer?”
- Simon Brown
8
http://www.codingthearchitecture.com/2014/07/06/distributed_big_balls_of_mud.html

9. 9
WTF?!?!
* where to focus?

10. “Software that
fits in your head”
- Daniel Terhorst-North
10
https://speakerdeck.com/tastapod/microservices-software-that-fits-in-your-head?slide=62

11. 11
“Software that
fits in our heads”

12. 4 key metrics: ‘Accelerate’
12
lead time
deployment frequency
mean time to restore (MTTR)
change fail percentage

13. Software that is ‘too big for
our heads’ works against
organizational agility
13

14. Team Cognitive Load
14

15. COGNITIVE LOAD:
The total amount of
mental effort being used
in the working memory
- John Sweller
15

16. Intrinsic
Extraneous
Germane
16
“How are
classes
defined in
Java?”

17. Intrinsic
Extraneous
Germane
17
“How do I
deploy this
app,
again?”

18. Intrinsic
Extraneous
Germane
18
“How do
bank
transfers
work?”

19. Intrinsic (skills)
Extraneous (mechanism)
Germane (domain focus)
19

20. (Intrinsic)
] Extraneous [
Germane
20

21. More: ‘Hacking Your Head’
21
Jo Pearce
(@jdpearce)
https://www.slideshare.net/JoPearce5/hacking-your-head-managing-information-overload-extended

22. Limit the size of software
services/products to the
cognitive load that the
team can handle.
22

23. 23
“Software that
fits in our heads”

24. A ‘team-first’
approach to software
boundaries
24

25. Team size ≲ 9 *
* possibly 15
25

26. 26
Each service must be fully
owned by a team with
sufficient cognitive capacity
to build and operate it.

27. Whole-team
techniques (mobbing)
27

28. Well-chosen domain
boundaries (DDD)
28

29. Developer Experience
#DevEx
29

30. Operator Experience
#operability
30

31. Thinnest Viable Platform
(TVP)
31

32. 4 fundamental topologies
32
Stream-aligned team
Enabling team
Complicated Subsystem team
Platform team

33. 4 fundamental topologies
33
Flow of change

34. 34
Team Interactions

35. 35
Team Interactions
3 defined Interaction Modes

36. 36
Team Interactions
Collaboration: 2 teams working together

37. 37
Team Interactions
X-as-a-Service: 1 provides, 1 consumes

38. 38
Team Interactions
Facilitating: 1 team helps another

39. 39
Team Interactions
3 defined Interaction Modes
Collaboration: 2 teams working together
X-as-a-Service: 1 provides, 1 consumes
Facilitating: 1 team helps another
@matthewpskelton / @TeamTopologies

40. 3 core interaction modes
40
Flow of change
X-as-a-Service
Facilitating
Collaboration

41. 41
Rapid flow of change

42. 42
Rapid feedback from
running systems

43. 43

44. 44

45. 45
Handovers (can) kill flow

46. 46
Team ownership must include:
Releasability
Testability
Operability / Supportability

47. 47

48. 48
→ flow of change → →

49. 49

50. 50

51. “...trend analysis, simulations, rapid
prototyping, scenario planning,
gaming, environmental scanning
… give clues to the context and
competitive environment.”
- Dr. Naomi Stanford,
“Guide to Organisation Design” (The Economist)
51

52. Case Studies
52

53. CaseStudy
53

54. CaseStudy
54
2016
(early)

55. CaseStudy
55
2016
(late)
CMS

56. CaseStudy
Framework
56
2017
(early)
CMS
Products

57. CaseStudy
Framework
57
Products
2017
(late)
CMS

58. Team became too large
⇔
System became monolithic
Blocked flow of work across streams
58

59. Listen to ‘triggers for evolution’
❏ Software grows too large
❏ Over specialization (Brent)
❏ Increased coordination needs
59

60. CaseStudy
60

61. CaseStudy
61
CD Enablement
Infrastructure
Automation
Test
Automation
Build & CI
Support

62. CaseStudy
62
CD Enablement Infrastructure
Automation
Test
Automation
Build & CI
Support

63. It’s not always about software size...
More broadly, align size and number
of domains of responsibility
with team cognitive capacity.
63

64. Aim for teams with high cohesion internally
(think autonomy, mastery & purpose)
Aim for low bandwidth comms
between smaller teams
64

65. Listen to ‘triggers for evolution’
❏ Awkward interactions
❏ People not invested, burn out
❏ Frequent context switching
65

66. Getting started with
team cognitive load
66

67. How well can the team as a unit “grok”
the systems they own and develop?
Explicit cognitive load
67

68. Push some things into a Platform?
Explicit cognitive load
68

69. Are skills or capabilities missing?
Explicit cognitive load
69

70. What would change if we adopted the
3 team interaction patterns?
Collaboration, X-as-a-Service, Facilitating
Team Interactions
70

71. Collaboration, X-as-a-Service, Facilitating
How would teams react & behave?
Team Interactions
71

72. How is your Platform defined?
Thinnest Viable Platform
72

73. What is the thinnest platform that
could work?
Thinnest Viable Platform
73

74. What’s needed to run and support it?
Thinnest Viable Platform
74

75. Team Topologies
75
Organizing business and
technology teams for fast flow
Matthew Skelton & Manuel Pais
IT Revolution Press
Order via stores worldwide: teamtopologies.com/book

76. Training
76
Day 1
Fundamentals
Day 2
Deep Dive
Day 3
Applying in Context
teamtopologies.com/training

77. Looking for case studies
77
Global manufacturing company
Large government agency
Global financial services

78. Remaining problems
78
Measuring cognitive load at scale
Assessing team communication at scale
How to nudge managers and heads of X
to become Team Topologies enablers

79. TeamTopologies.com
@TeamTopologies
Sign up for news and tips:
TeamTopologies.com

80. Thank you!
teamtopologies.com
80
Matthew Skelton, Conflux
@matthewpskelton
Manuel Pais, Independent
@manupaisable
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