From Legacy to Cloud

A journey from monolithic, on-premise, customized, legacy software to cloud-native, multi-tenant, domain-driven SAAS.

Transcript

1. Starring
   Directed By
   Special
   Appearance
   Presented by
   With
   

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6. 👨💻👨🏫👨💼
   

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7. @hschwentner
   

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8. Alphorn
   Auto Leasing Inc.
   

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10. Springfield
    Duckburg
    Metropolis
    

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11. Monolease A
    

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12. Springfield
    Duckburg
    Metropolis
    1.0
    1.1
    1.0a
    

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13. Springfield
    Duckburg
    Metropolis
    Twin Peaks
    1.1
    1.0
    1.1
    1.0a
    

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14. =>
    cloud
    on-premise to
    

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15. @hschwentner
    Mistake: Move to the cloud because
    some random dude at a
    conference said so
    Better: Move to the cloud because
    that solves an actual
    problem
    

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16. Springfield
    Duckburg
    Metropolis
    Leas-
    N-dary
    

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17. Springfield
    Duckburg
    Twin Peaks
    Metropolis
    Leas-
    N-dary
    

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18. Springfield
    Duckburg
    Twin Peaks
    Metropolis
    Leas-
    N-dary
    2.0
    

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19. @hschwentner
    Mistake: Continue working like you
    always did
    Better: Change your mindset
    

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20. product
    project to
    =>
    

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21. =>
    agile
    waterfall to
    

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22. Individuals and interactions
    over processes and tools
    Customer collaboration
    over contract negotiation
    Working software
    over comprehensive documentation
    Responding to change
    over following a plan
    Agile
    Manifesto
    

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23. =>
    micro-
    services
    monolith to
    

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24. @hschwentner
    Mistake: Transform the whole
    system at once
    Better: Move in baby steps
    

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25. old old old old
    new
    new new new
    “just flip
    the lever”
    1 2 3 4 5
    a.k.a.
    big bang
    replacement
    

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26. old old old
    new
    new new new
    2 3 4 5
    old
    1
    

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27. Strangler
    Fig
    Application
    

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28. Strangler Fig Application
    

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29. Lesson:
    is better than
    Strangler Fig
    Application
    Big Bang
    Replacement
    

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30. =>
    micro-
    services
    monolith
    buy
    to
    carve out
    build
    new
    

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31. Read on in:
    

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32. big ball
    of mud
    =>
    strategic
    design
    to
    

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33. @hschwentner
    Mistake: Cutting the system by
    technical reasons
    Better: Cutting the system into
    bounded contexts
    

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34. =>
    tactical
    design
    anemic
    domain model to
    value
    object
    entity
    repository
    impleme-
    ntation
    

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35. behavior
    data to
    1001010011
    1110010110
    0010011101
    calculatePrice()
    assessRisk()
    signContract()
    

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36. Eric
    Evans
    Read on in:
    

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37. Individuals and interactions
    over processes and tools
    Customer collaboration
    over contract negotiation
    Working software
    over comprehensive documentation
    Responding to change
    over following a plan
    Agile
    Manifesto
    

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38. doctor
    waiter to
    =>
    What are
    your
    orders?
    What is
    your
    problem?
    

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39. @hschwentner
    Mistake: Thinking that it’s about
    software
    Better: Realizing that it’s about
    business
    

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40. business
    enabling
    =>
    technology-
    centered
    to
    

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41. What's the most
    impactful thing
    we can do next?
    

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42. Software
    != End in itself
    

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43. customer
    tells wish for
    1
    salesperson
    signs
    to
    gives
    for
    contract
    3
    risk manager
    contract
    passes on
    to
    4
    contract
    votes
    checks
    calculates
    5
    6
    7
    calculates
    to
    8
    2
    car
    credit
    rating
    installment
    car
    resale
    value
    contract
    

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44. https://domainstorytelling.org
    Read on in:
    

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45. @hschwentner
    Lesson:
    1. First understand the business
    2. Only then build software
    

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46. @hschwentner
    Lesson:
    1. First learn about the problem
    2. Only then look for a solution
    

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47. @hschwentner
    What is Software?
    technical
    system
    socio-
    +
    

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48. “Organizations which design systems
    are constrained to produce designs
    which are copies of the
    communication structures of
    these organizations.”
    Melvin Conway
    

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49. @hschwentner
    Mistake: Ignoring team
    organization
    Better: Respect Conway’s law
    

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50. =>
    micro-
    services
    monolith to
    cross-
    functional
    teams
    

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51. Alignment
    technical
    business-wise
    organizational
    technical
    business-wise
    organizational
    

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52. Read on in:
    

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53. Individuals and interactions
    over processes and tools
    Customer collaboration
    over contract negotiation
    Working software
    over comprehensive documentation
    Responding to change
    over following a plan
    Agile
    Manifesto
    

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54. user dev
    

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55. @hschwentner
    Mistake: Misunderstand your users
    Better: Build a common language
    

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56. @hschwentner
    🧑💼
    👨💻
    👨💼
    have to understand
    The single most important fact in
    software development:
    Tech people
    business people.
    👩💼
    👩💻
    

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57. =>
    direct
    commu-
    nication
    telephone
    game
    to
    user
    dev
    user dev
    

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58. finance
    dev
    user
    sales
    PO
    HR
    management
    marketing
    scrum master
    UX
    

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59. Individuals and interactions
    over processes and tools
    Customer collaboration
    over contract negotiation
    Working software
    over comprehensive documentation
    Responding to change
    over following a plan
    Agile
    Manifesto
    

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60. It’s a full team sport
    Photo: Bart Derksen/Wikipedia
    

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61. @hschwentner
    Mistake: Thinking “We’re never
    gonna make it”
    

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62. We can
    do it,
    too!
    

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63. @hschwentner
    Mistake: Going on the journey alone
    Better:
    

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66. Bibliography
    Beck, Kent et al. Manifesto for Agile Software Development. 2001.
    Conway, Melvin E. “How Do Committees Invent?” Datamation 14, no. 5 (April 1968): 28–31.
    Evans, Eric. Domain-Driven Design: Tackling Complexity in the Heart of Software. Boston: Addison-Wesley, 2004.
    Feathers, Michael C. Working Effectively with Legacy Code. Upper Saddle River, NJ: Prentice Hall, 2004.
    Foote, Brian and Joseph Yoder. “Big Ball of Mud.” PLoP ’97, Monticello, IL, September 1997.
    Fowler, Martin. Refactoring: Improving the Design of Existing Code. 2nd ed. Boston: Addison-Wesley, 2019.
    Fowler, Martin. “Strangler Fig Application.” Bliki, June 29, 2004.
    Hofer, Stefan and Henning Schwentner. Domain Storytelling: a Collaborative, Visual, and Agile Way to Develop
    Domain-Driven Software. Boston: Addison-Wesley, 2022.
    Kaur, Ravneet. “Agile Teams—Are They Waiters or Doctors?” LinkedIn. April 1, 2019.
    Kernighan, Brian W. Software Tools in Pascal. Addison-Wesley, 1981.
    Newman, Sam. Monolith to Microservices: Evolutionary Patterns to Transform Your Monolith. Sebastopol, CA:
    O’Reilly, 2021.
    Skelton, Matthew and Manuel Pais. Team Topologies: Organizing Business and Technology Teams for Fast Flow.
    Portland, OR: IT Revolution, 2019.
    Weinberg, Gerald M. The Secrets of Consulting. New York: Dorset House, 1985.
    

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68. Henning Schwentner
     https://hschwentner.io
     @hschwentner
    ✉ hs@wps.de
    

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