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 I explain how and why.

1. TeamTopologies.com
@TeamTopologies
Forget ‘Monoliths vs Microservices’; focus on
Team Cognitive Load
Manuel Pais
co-author of Team Topologies
@manupaisable
DevOps Perth - 9 Sep 2020

2. 2
Manuel Pais
Independent IT organizational consultant and trainer
Ex-dev, ex-build manager, ex-tester, ex-QA lead
LinkedIn instructor on Accelerating Continuous Delivery
Twitter: @manupaisable
LinkedIn: manuelpais

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. 4
Team Cognitive Load
Team-First Approach
Case Studies
Getting started

5. Team Cognitive Load
5

6. 6

7. “Start with monolith and
extract microservices.”
- Tammer Saleh
7
https://www.infoq.com/presentations/cloud-anti-patterns

8. “Don’t start with a
monolith when your goal is
a microservices
architecture”
- Stefan Tilkov
8
http://martinfowler.com/articles/dont-start-monolith.html

9. “If you can't build a
monolith, what makes you
think microservices are
the answer?”
- Simon Brown
9
http://www.codingthearchitecture.com/2014/07/06/distributed_big_balls_of_mud.html

10. 10
WTF?!?!
* where to focus?

11. “Software that
fits in your head”
- Daniel Terhorst-North
11
https://speakerdeck.com/tastapod/microservices-software-that-fits-in-your-head?slide=62

12. 12
“Software that
fits in our heads”

13. 4 key metrics: ‘Accelerate’
13
lead time
deployment frequency
mean time to restore (MTTR)
change fail percentage

14. Software that is ‘too big for
our heads’ works against
organizational agility
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. 24
Team cognitive load as
a key consideration for
org decisions

25. Team-First Approach
35

26. A ‘team-first’
approach to delivery
of digital products
36

27. Team size ≲ 9 *
* possibly 15
37

28. Well-chosen streams
& domain boundaries
39

29. 40

30. 41

31. 42
Feature

32. 43
Types of streams
● a service
● a set of features
● a user persona or user journey
● a compliance standard
● a specific market or geography
● ...

33. Developer Experience
#DevEx
45

34. Operator Experience
#operability
46

35. Modern Platform
as a Product
47

36. 4 fundamental topologies
48
Stream-aligned team
Enabling team
Complicated Subsystem team
Platform team

37. 4 fundamental topologies
49
Flow of change

38. 3 core interaction modes
50
Flow of change
X-as-a-Service
Facilitating
Collaboration

39. 51
Rapid flow of change

40. 52
Rapid feedback from
running systems

41. 53

42. 54

43. 55
Handovers (can) kill flow

44. 56
Each service must be fully
owned by a team with
sufficient cognitive capacity
to build and operate it.

45. 57
Team ownership must include:
Releasability
Testability
Operability / Supportability

46. 58

47. 59

48. Case Studies
63

49. “...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)
64

50. CaseStudy
65

51. CaseStudy
66
2016
(early)

52. CaseStudy
67
2016
(late)
CMS

53. CaseStudy
Framework
68
2017
(early)
CMS
Products

54. CaseStudy
Framework
69
Products
2017
(late)
CMS

55. CaseStudy
Framework
70
Products
2017
(early)
CMS

56. Team became too large
⇔
System became monolithic
Blocked flow of work across streams
71

57. Listen to ‘triggers for evolution’
❏ Software grows too large
❏ Over specialization (Brent)
❏ Increased coordination needs
72

58. CaseStudy
73

59. CaseStudy
74
CD Enablement
Infrastructure
Automation
Test
Automation
Build & CI
Support

60. CaseStudy
75
CD Enablement Infrastructure
Automation
Test
Automation
Build & CI
Support

61. It’s not always about software size...
More broadly, align size and number
of domains of responsibility
with team cognitive capacity.
76

62. Aim for teams with high cohesion internally
(think autonomy, mastery & purpose)
Aim for low bandwidth comms
between smaller teams
77

63. Listen to ‘triggers for evolution’
❏ Awkward interactions
❏ People not invested, burn out
❏ Frequent context switching
78

64. Getting started
79

65. Getting started
80
Explicit cognitive load

66. How well can the team as a unit “grok”
the systems they own and develop?
Explicit cognitive load
81

67. 82

68. Push some things into a Platform?
Explicit cognitive load
83

69. Are skills or capabilities missing?
Explicit cognitive load
84

70. Getting started
85
Explicit cognitive load
Misaligned work streams
Team Interactions
Thinnest Viable Platform

71. Does it frequently take three or more
teams to change a single user journey?
Misaligned work streams
86

72. Are development teams assumed to
know and comply with regulations?
Misaligned work streams
87

73. Getting started
89
Team interactions

74. Do we know which teams we need to
interact with? What outcomes do we
expect from the interaction?
Collaboration, X-as-a-Service, Facilitating
Team Interactions
90

75. Getting started
91
Explicit cognitive load
Misaligned work streams
Team interactions

76. Team Topologies
92
Organizing business and
technology teams for fast flow
Matthew Skelton & Manuel Pais
IT Revolution Press
Order via stores worldwide: teamtopologies.com/book

77. TeamTopologies.com
@TeamTopologies
teamtopologies.com/news
Team Topologies
Essentials Training
Oct 7, 8, 14, 15 (APAC friendly)
Details: teamtopologies.com/events
4 half-day online sessions with Manuel Pais
10% discount code TTDEVOPSPERTH10

78. Resources
97
teamtopologies.com/resources
(links, slides, video)
github.com/teamtopologies
(templates, assessments, etc)

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

80. Thank you!
100
Matthew Skelton, Conflux
@matthewpskelton
Manuel Pais, Independent
@manupaisable
teamtopologies.com