Independent Service Heuristics
a rapid, business-friendly approach to
flow-oriented boundaries
DDD EU 2022
Matthew Skelton (Conflux) and Nick Tune (Independent)
Slide 2
Slide 2 text
How the Independent
Service Heuristics (ISH)
work and why you might
want to try them
(to help find good boundaries for flow)
2
Slide 3
Slide 3 text
Biogs
Matthew Skelton
Founder at Conflux -
confluxhq.com
Co-author the book
‘Team Topologies’
@matthewpskelton
Nick Tune
Independent -
ntcoding.co.uk
Author of the book
‘Architecture
Modernization’
@ntcoding
3
Slide 4
Slide 4 text
●
What are ISH & what do they do?
●
Experience with ISH - Nick
●
Experience with ISH - Matthew
●
Takeaway points
4
Slide 5
Slide 5 text
What are the Independent
Service Heuristics?
What do they do?
5
Slide 6
Slide 6 text
“The Independent Service Heuristics (ISH)
are rules-of-thumb (clues) for identifying
candidate value streams and domain
boundaries by seeing if they could be run as a
separate SaaS/cloud product.”
6
teamtopologies.com/ish
Slide 7
Slide 7 text
Independent Service Heuristics
evolved through helping 40+
customer organizations adopt
Team Topologies since 2018 🌐
7
Slide 8
Slide 8 text
ISH principle #1
8
Flow-friendly
boundaries
Slide 9
Slide 9 text
Good boundaries in 2022 are
optimized for fast flow.
9
Slide 10
Slide 10 text
DDD was originally not
designed explicitly to work
well with fast flow:
DDD was “pre-cloud”.
10
Slide 11
Slide 11 text
ISH principle #2
11
Business-friendly
language
Slide 12
Slide 12 text
DDD terminology and
approaches can be baffling
and inaccessible for many
people.
12
Slide 13
Slide 13 text
ISH principle #3
13
Promote group
discussion and learning
Slide 14
Slide 14 text
Coherence in concepts and
terminology emerges through
group learning sessions (a
shared experience).
14
Slide 15
Slide 15 text
ISH principle #4
15
Rapid results needed
Slide 16
Slide 16 text
ISH is a rapid, ‘low-fidelity’
approach for fast flow
boundaries that can benefit
from using DDD alongside for
further insights.
16
Slide 17
Slide 17 text
Independent Service Heuristics
1. Sense-check: Could it make any logical sense to offer this thing "as a service"?
2. Brand: Could you imagine this thing branded as a public cloud service (like AvocadoOnline.com
🥑
)?
3. Revenue/Customers: Could this thing be managed as a viable cloud service in terms of revenue and
customers?
4. Cost tracking: Could the organisation currently track costs and investment in this thing separately from
similar things?
5. Data: Is it possible to define clearly the input data (from other sources) that this things needs?
6. User Personas: Could this thing have a small/well-defined set of user types or customers (user personas)?
7. Teams: Could a team or set of teams effectively build and operate a service based on this thing?
8. Dependencies: Would this team be able to act independently of other teams for the majority of the time
to achieve their objectives?
9. Impact/Value: Would the scope of this thing provide a team with an impactful and engaging challenge?
10. Product Decisions: Would the team working on this thing be able to "own" their own product roadmap
and the product direction?
17
https://github.com/TeamTopologies/Independent-Service-Heuristics
Slide 18
Slide 18 text
Independent Service Heuristics
1 - Sense-check: Could it make any logical sense to offer this
thing "as a service"?
a. Is this thing independent enough?
b. Would consumers understand or value it?
c. Would it simplify execution?
18
Slide 19
Slide 19 text
Independent Service Heuristics
2 - Brand: Could you imagine this thing branded as a public
cloud service (like AvocadoOnline.com
🥑
)?
a. Would it be a viable business (or "micro-business") or
service?
b. Would it be a compelling offering?
c. Could a marketing campaign be convincing?
19
Slide 20
Slide 20 text
20
Slide 21
Slide 21 text
21
Slide 22
Slide 22 text
22
Slide 23
Slide 23 text
23
Slide 24
Slide 24 text
24
Slide 25
Slide 25 text
25
Slide 26
Slide 26 text
26
Slide 27
Slide 27 text
27
Slide 28
Slide 28 text
28
Slide 29
Slide 29 text
29
Slide 30
Slide 30 text
Independent Service Heuristics
3 - Revenue/Customers: Could this thing be managed as a viable
cloud service in terms of revenue and customers?
4 - Cost tracking: Could the organisation currently track costs
and investment in this thing separately from similar things?
5 - Data: Is it possible to define clearly the input data (from other
sources) that this things needs?
30
Slide 31
Slide 31 text
Independent Service Heuristics
6 - User Personas: Could this thing have a small/well-defined set
of user types or customers (user personas)?
7 - Teams: Could a team or set of teams effectively build and
operate a service based on this thing?
8 - Dependencies: Would this team be able to act independently
of other teams for the majority of the time to achieve their
objectives?
31
Slide 32
Slide 32 text
Independent Service Heuristics
9 - Impact/Value: Would the scope of this thing provide a team
with an impactful and engaging challenge?
10 - Product Decisions: Would the team working on this thing be
able to "own" their own product roadmap and the product
direction?
32
Slide 33
Slide 33 text
What are these ISH
questions actually doing?
33
Slide 34
Slide 34 text
34
Viability
Slide 35
Slide 35 text
35
Existing SaaS
Slide 36
Slide 36 text
36
Decoupled?
Slide 37
Slide 37 text
37
Outsource-able?
Slide 38
Slide 38 text
38
Use biz expertise
Slide 39
Slide 39 text
39
Hinting at Haier
Slide 40
Slide 40 text
ISH uses intuition and
experience from domain
experts and engineers to
explore viable services
40
Slide 41
Slide 41 text
Experience with ISH - Nick
41
Slide 42
Slide 42 text
Case Study:
North-American
ecommerce market leader
Health-related industry
Regulatory obstacles
Ambitious growth
42
Slide 43
Slide 43 text
Why I Decided to Use ISH
43
Slide 44
Slide 44 text
Validate & Refine: Are These Good Boundaries?
44
Slide 45
Slide 45 text
Iteratively Identifying Value Streams
45
Credit: Team Topologies Academy
academy.teamtopologies.com/courses/independent-value-streams-with-domain-driven-design
Slide 46
Slide 46 text
Biz Context: Single to Multiple Verticals
46
Slide 47
Slide 47 text
Biz Context: Landscape Evolution
47
Slide 48
Slide 48 text
Biz Context: Do We Need Horizontals?
48
Slide 49
Slide 49 text
Biz Context: Growing Pains
49
Slide 50
Slide 50 text
Phase 1: Discovery and Modelling
50
Slide 51
Slide 51 text
ISH: 1. Sense Check, 2. Brand
51
Slide 52
Slide 52 text
ISH: 3. Revenue/Customers, 6. Personas
52
Slide 53
Slide 53 text
ISH: 9. Impact/Value
53
Slide 54
Slide 54 text
ISH: 5. Data
54
Slide 55
Slide 55 text
ISH: 7. Teams, 8. Dependencies
55
Slide 56
Slide 56 text
ISH: 4. Cost Tracking, 10. Product Decisions
56
Slide 57
Slide 57 text
“Just the phrase 'independent enough' made
us really think deeply about what level of
coupling is acceptable for this domain
especially with future evolution in mind.”
– Senior Engineering Manager
57
Slide 58
Slide 58 text
“This ISH session introduced me to a lot of
new concepts that I never realised were so
relevant to software architecture.”
– Software Developer
58
Slide 59
Slide 59 text
Experience with ISH -
Matthew
59
Slide 60
Slide 60 text
Case Study:
North-American
ecommerce market leader
Health-related industry
Regulatory obstacles
Ambitious growth
60
Slide 61
Slide 61 text
Execs: on-board but unrealistic
61
~ “When I was building
ecommerce sites 20 years ago,
it was much quicker and
simpler … The engineers
obsess over details…”
Slide 62
Slide 62 text
Execs: on-board but unrealistic
62
~ “We want to see results in a
few hours … How hard can it
be to find some team
boundaries?”
Slide 63
Slide 63 text
Our approach: visual “heat-map”
63
Immediate sense of
consensus or ambiguity.
Identify areas for splitting off
or further investigation.
Slide 64
Slide 64 text
“I really like using the ISH as a rule of
thumb for where we draw high level
boundaries w/in the org.”
– Head of Strategy
64
Slide 65
Slide 65 text
“... this is how we can build
teams that are as independent as
possible while maintaining laser like
focus on outcomes …”
– Head of Strategy
65
Slide 66
Slide 66 text
We used Independent
Service Heuristics to help
people realize what is
involved in finding good
boundaries for fast flow
66
Slide 67
Slide 67 text
Case Study:
Large retailer in
South-East Asia
Differentiating via
digital services
67
Slide 68
Slide 68 text
Wide spectrum of roles participating
68
●
Engineering directors
●
Engineers
●
Head of SRE (reliability)
●
Product directors - physical goods
●
Product directors - digital services
●
CTO
●
Warehouse manager
Slide 69
Slide 69 text
ISH bridged physical and
digital product needs
69
checkout flow, High Net Worth customers, order picking,
returns, shipping & fulfilment, warehouse management, …
Slide 70
Slide 70 text
Our approach: visual “heat-map”
70
Slide 71
Slide 71 text
“The framework and shared language
[of] ISH … was transformational to the
discussions … about our organisation
and team structure.”
– Head of Product
71
Slide 72
Slide 72 text
“Thanks to the Team Topologies and
ISH framework our team structure is
more autonomous, meaningful, and
productive.”
– Head of Product
72
Slide 73
Slide 73 text
Biz and product people often
have an intuitive lightbulb
moment 💡 with ISH and
become enthusiastic
73
Slide 74
Slide 74 text
Takeaway points - ISH
74
Slide 75
Slide 75 text
ISH is a rapid, ‘low-fidelity’
approach for fast flow
boundaries that can benefit
from using DDD alongside for
further insights.
75
Slide 76
Slide 76 text
Going through the ISH
heuristics raised important
topics that focusing on the
domain only didn’t surface
76
Slide 77
Slide 77 text
People would often mention
heuristics in meetings - they
started to become ingrained in
day-to-day thinking
77
Slide 78
Slide 78 text
We did design with a diverse
group and didn’t need to
introduce much theory or
explain weird terminology
78
Slide 79
Slide 79 text
Nick was skeptical of not
starting with Event Storming -
but the ISH discovery
workshop had high
engagement and enthusiasm.
79
Slide 80
Slide 80 text
ISH increases practitioner and
manager-level awareness of
“service-oriented” - the
business reasons for a change
(rather than making changes to “an IT system” that
happens to be easy to deploy)
80
Slide 81
Slide 81 text
Biz and product people often
have an intuitive lightbulb
moment 💡 with ISH and
become enthusiastic
81
Slide 82
Slide 82 text
ISH addresses many dimensions
for flow-friendly boundaries:
viability, (de)coupling, existing
SaaS, outsource-able, Haier-style
micro enterprises, …
82
Slide 83
Slide 83 text
Try the Independent Service
Heuristics (ISH):
teamtopologies.com/ish
83
Slide 84
Slide 84 text
Thank you
Matthew Skelton
Founder at Conflux -
confluxhq.com
@matthewpskelton
Nick Tune
Independent -
ntcoding.co.uk
@ntcoding
84
teamtopologies.com/ish