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. Key takeaways: - What is team cognitive load and why that matters - Using team cognitive load as the guiding principle for sustainable ownership and evolution of software systems - What are the fundamental topologies and interaction modes that help reduce cognitive load

1. TeamTopologies.com
@TeamTopologies
Forget ‘Monoliths vs Microservices’; start with
Team Cognitive Load
Manuel Pais
co-author of Team Topologies
@manupaisable
London Microservices Meetup - 18 Nov 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 (mechanisms)
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. 44
Domain-Driven
Design

34. 45
DDD-Lite™*
Independent Service Heuristics
* only joking

35. Independent Service Heuristics
46
https://github.com/TeamTopologies/Independent-Service-Heuristics

36. Developer Experience
#DevEx
47

37. Operator Experience
#operability
48

38. Modern Platform
as a Product
49

39. 4 fundamental topologies
50
Stream-aligned team
Enabling team
Complicated Subsystem team
Platform team

40. 4 fundamental topologies
51
Flow of change

41. 3 core interaction modes
52
Flow of change
X-as-a-Service
Facilitating
Collaboration

42. 53
Rapid flow of change

43. 54
Rapid feedback from
running systems

44. 58
Each service must be fully
owned by a team with
sufficient cognitive capacity
to build and operate it.

45. 59
Team ownership must include:
Releasability
Testability
Operability / Supportability

46. 60

47. 61

48. Case Study
65

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)
66

50. CaseStudy
67

51. CaseStudy
68
2016
(early)

52. CaseStudy
69
2016
(late)
CMS

53. CaseStudy
Framework
70
2017
(early)
CMS
Products

54. CaseStudy
Framework
71
Products
2017
(late)
CMS

55. CaseStudy
Framework
72
Products
2017
(early)
CMS

56. Team became too large
⇔
System became too large for team
Blocked flow of work across streams
73

57. Listen to ‘triggers for evolution’
❏ Software grows too large
❏ Over specialization (Brent)
❏ Increased coordination needs
74

58. Getting started
81

59. Getting started
82
Explicit cognitive load

60. How well can the team as a unit “grok”
the systems they own and develop?
Explicit cognitive load
83

61. 84

62. Push some things into a Platform?
Explicit cognitive load
85

63. Are skills or capabilities missing?
Explicit cognitive load
86

64. Getting started
87
Explicit cognitive load
Misaligned work streams
Team Interactions
Thinnest Viable Platform

65. Does it frequently take three or more
teams to change a single user journey?
Misaligned work streams
88

66. Are development teams assumed to
know and comply with regulations?
Misaligned work streams
89

67. Getting started
91
Team interactions

68. 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
92

69. Getting started
93
Explicit cognitive load
Misaligned work streams
Team interactions

70. Team Topologies
94
Organizing business and
technology teams for fast flow
Matthew Skelton & Manuel Pais
IT Revolution Press
Order via stores worldwide: teamtopologies.com/book

71. Workbook
coming soon...
Team Topologies
for Remote Teams
95
for Remote
Teams
Sign up for news: teamtopologies.com/newsletter
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72. Remote-
Friendly
Training
🠊 teamtopologies.com/training
96

73. Resources
98
teamtopologies.com/resources
(links, slides, video)
github.com/teamtopologies
(templates, assessments, etc)

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

75. Thank you!
101
Matthew Skelton, Conflux
@matthewpskelton
Manuel Pais, Independent
@manupaisable
teamtopologies.com