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, illustrated by real case studies.

1. TeamTopologies.com
@TeamTopologies
Forget ‘Monoliths vs Microservices’; focus on
Team Cognitive Load
Matthew Skelton & Manuel Pais
co-authors of Team Topologies
@matthewpskelton @manupaisable
DevOps Enterprise Summit EUR 2019 - 26 June

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
Publication date: Sept 2019
IT Revolution Press
Pre-order from Amazon:
https://teamtopologies.com/book

4. 4
Book signing ✍
Weds 26 June
@ 19:30

5. Monoliths vs
Microservices
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. Team Cognitive Load
15

16. COGNITIVE LOAD:
The total amount of
mental effort being used
in the working memory
- John Sweller
16

17. Intrinsic
Extraneous
Germane
17
“How are
classes
defined in
Java?”

18. Intrinsic
Extraneous
Germane
18
“How do I
deploy this
app,
again?”

19. Intrinsic
Extraneous
Germane
19
“How do
bank
transfers
work?”

20. Intrinsic (skills)
Extraneous (mechanism)
Germane (domain focus)
20

21. (Intrinsic)
] Extraneous [
Germane
21

22. More: ‘Hacking Your Head’
22
Jo Pearce
(@jdpearce)
https://www.slideshare.net/JoPearce5/hacking-your-head-managing-information-overload-extended

23. Limit the size of software
services/products to the
cognitive load that the
team can handle.
23

24. 24
“Software that
fits in our heads”

25. A ‘team-first’
approach to software
boundaries
25

26. Team size ≲ 9 *
* possibly 15
26

27. 27
Each service must be fully
owned by a team with
sufficient cognitive capacity
to build and operate it.

28. Whole-team
techniques (mobbing)
28

29. Well-chosen domain
boundaries (DDD)
29

30. Developer Experience
#DevEx
30

31. Operator Experience
#operability
31

32. Thinnest Viable Platform
(TVP)
32

33. 4 fundamental topologies
33
Stream-aligned team
Enabling team
Complicated Subsystem team
Platform team

34. 4 fundamental topologies
34
Flow of change

35. 3 core interaction modes
35
Flow of change
X-as-a-Service
Facilitating
Collaboration

36. Case Studies
36

37. CaseStudy
37

38. CaseStudy
38
2016
(early)

39. CaseStudy
39
2016
(late)
CMS

40. CaseStudy
Framework
40
2017
(early)
CMS
Products

41. CaseStudy
Framework
41
Products
2017
(late)
CMS

42. Team became too large
⇔
System became monolithic
Blocked flow of work across streams
42

43. Listen to ‘triggers for evolution’
❏ Software grows too large
❏ Over specialization (Brent)
❏ Increased coordination needs
43

44. CaseStudy
44

45. CaseStudy
45
CD Enablement
Infrastructure
Automation
Test
Automation
Build & CI
Support

46. CaseStudy
46
CD Enablement Infrastructure
Automation
Test
Automation
Build & CI
Support

47. It’s not always about software size...
More broadly, align size and number
of domains of responsibility
with team cognitive capacity.
47

48. Aim for teams with high cohesion internally
(think autonomy, mastery & purpose)
Aim for low bandwidth comms between
smaller teams
48

49. Listen to ‘triggers for evolution’
❏ Awkward interactions
❏ People not invested, burn out
❏ Frequent context switching
49

50. CaseStudy

51. Getting started with
team cognitive load
51

52. How well can the team as a unit “grok”
the systems they own and develop?
Explicit cognitive load
52

53. Push some things into a Platform?
Explicit cognitive load
53

54. Are skills or capabilities missing?
Explicit cognitive load
54

55. What would change if we adopted the
3 team interaction patterns?
Collaboration, X-as-a-Service, Facilitating
Team Interactions
55

56. Collaboration, X-as-a-Service, Facilitating
How would teams react & behave?
Team Interactions
56

57. How is your Platform defined?
Thinnest Viable Platform
57

58. What is the thinnest platform that
could work?
Thinnest Viable Platform
58

59. What’s needed to run and support it?
Thinnest Viable Platform
59

60. Team Topologies
60
Organizing business and
technology teams for fast flow
Matthew Skelton & Manuel Pais
Publication date: Sept 2019
IT Revolution Press
Pre-order via stores worldwide:
teamtopologies.com/book

61. Training
61
Day 1
Fundamentals
Day 2
Deep Dive
Day 3
Applying in Context
teamtopologies.com/training

62. Sign up for news and tips:
TeamTopologies.com
62

63. Thank you!
teamtopologies.com
63
Matthew Skelton, Conflux
@matthewpskelton
Manuel Pais, Independent
@manupaisable
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