The strategies behind ddd – AdeoDevSummit 2022

Have you ever experienced that a small change in the business triggers an apocalyptic change in the software code? These kinds of symptoms are often a symptom of software architecture and business misalignment.
In this talk we will see how to enable developers to express business concerns in the software architecture in order to prevent a wide range of problems. Issues that cause particularly harmful side-effects and can prevent an efficient refactoring policy.
This introduction to the strategic aspects of Domain Driven Design is not a purely technical presentation, and is therefore aimed at both developers and all stakeholders involved in software design.

Transcript

1. www.lilobase.me
   The strategies
   behind DDD
   @lilobase
   #DevSummit
   sundayapp.com
   

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2. Let’s start a new project !
   

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3. Sprint Zero
   Java or C# ?
   Spring Boot or
   Quarkus ?
   Kafka
   or Redis ?
   Microservices
   or Monolith ?
   Kubernetes
   or Nomad ?
   Angular
   or React ?
   

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4. Look, at our spring
   boot application with
   Kafka deployed on a K8S
   Cluster
   They know nothing
   about the project’s business
   domain
   …
   Sprint Zero
   

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5. Java or C# ?
   Spring Boot or
   Quarkus ?
   Kafka
   or Redis ?
   Microservices
   or Monolith ?
   Kubernetes
   or Nomad ?
   Angular
   or React ?
   These issues address only
   the solution
   

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6. But not the problem
   What should we do ?
   …
   

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7. Spring Boot or
   Quarkus ?
   Kafka
   or Redis ?
   Microservices
   or Monolith ?
   Kubernetes
   or Nomad ?
   Angular
   or React ?
   And that's why we
   
   
   are seen as technical expert
   Java or C# ?
   

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8. solution
   problem
   What should we do ?
   How are we going to do it ?
   It is an important discussion to have
   But only after we've
   fi
   gured out
   

   what to do
   

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9. DDD is all about
   Alignment
   What should we do ?
   How are we going to do it ?
   

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10. DDD is all about
    Alignment
    What should we do ?
    How are we going to do it ?
    

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11. « Give a child a hammer and
    everything they meets has to be
    pounded. »
    – Abraham Kaplan
    

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12. « We put the needs
    of the database
    before the needs of
    the users, which
    results in some
    pretty crappy
    experiences »
    – @WalterStephanie
    

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13. www.lilobase.me
    DDD is all about
    Understanding
    @lilobase
    

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14. Domains & Subdomains
    Business Domain discovery
    THE software
    

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15. Domain Mapping
    Business Domain Classi
    fi
    cation
    Authoring
    
    
    &
    
    
    Publishing
    Customer Care
    Printing &
    
    
    Supply Chain
    Retail Store
    You need to acknowledge the fact that
    you have several domains
    

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16. Domain Mapping
    Business Domain Classi
    fi
    cation
    Authoring
    
    
    &
    
    
    Publishing
    Customer Care
    Printing &
    
    
    Supply Chain
    Retail Store
    Only one VP should be
    
    
    angry at a time
    

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17. Domain Mapping
    Business Domain Classi
    fi
    cation
    Authoring
    
    
    &
    
    
    Publishing
    Customer Care
    Printing &
    
    
    Supply Chain
    Retail Store
    These are neither Bounded
    Contexts nor Microservices
    

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18. Domain Mapping
    Business Domain Classi
    fi
    cation
    Authoring
    
    
    &
    
    
    Publishing
    Customer Care
    Printing &
    
    
    Supply Chain
    Retail Store
    These are your domains
    

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19. Domain Mapping
    Business Domain Classi
    fi
    cation
    Authoring
    
    
    &
    
    
    Publishing
    Customer
    Care
    Printing &
    
    
    Supply Chain
    Online Retail Store
    Payment
    processor
    Catalogue Invoicing
    Your domains contain domains
    

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20. Supporting
    Subdomain
    Generic
    Subdomain
    Core
    (sub)Domain
    Key differentiator
    Domains & Subdomains
    Business Domain Classi
    fi
    cation
    Essential to the
    

    organization’s success
    Required for the
    

    organization’s success
    Critical to the
    

    organization’s success
    

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21. Domain Mapping
    Business Domain Classi
    fi
    cation
    Authoring
    Plateform
    Publishing &
    Printing
    Inventory
    Management
    Payment
    Processor
    Catalogue
    Invoicing
    Shipping
    Order
    Processing
    Proofreading
    

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22. Domains & Subdomains
    Business Domain Classi
    fi
    cation
    Authoring
    Plateform
    Inventory
    Management
    Shipping
    Payment
    Processor
    Catalogue
    Invoicing
    Order
    Processing
    Publishing &
    Printing
    Proofreading
    

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23. Domains & Subdomains
    Business Domain Classi
    fi
    cation
    Authoring
    Plateform
    Inventory
    Management
    Payment
    Processor
    Catalogue
    Invoicing
    Each business context is speci
    fi
    c
    Shipping
    Order
    Processing
    Publishing &
    Printing
    Proofreading
    

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24. Authoring
    Plateform
    Domains’ Connexion
    Reveal Business Relationships
    Inventory
    Management
    Shipping
    Catalogue
    Invoicing
    Order
    Processing
    Payment
    Processor
    It can highlight signi
    fi
    cant
    

    sub-domain
    Publishing &
    Printing
    Proofreading
    

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25. www.lilobase.me
    DDD is all about
    Context
    @lilobase
    

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26. From Problem to Solution
    Authoring
    Plateform
    Publishing
    & Printing
    Inventory
    Management
    Shipping
    Payment
    Processor
    Catalogue
    Invoicing
    Order
    Processing
    Proofreading
    

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27. From Problem to Solution
    Authoring
    Plateform
    Publishing
    & Printing
    Inventory
    Management
    Shipping
    Payment
    Processor
    Catalogue
    Invoicing
    Order
    Processing
    problem
    solution
    Payment
    processor
    Invoicing
    Order
    Processing
    Shipping
    Authoring
    Plateforme
    Inventory
    Management
    Catalogue
    Publishing
    Proofreading
    Proofreading
    Inventory E-commerce platform
    Authoring
    Publishing
    

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28. Domains & Subdomains
    Development Strategy
    Supporting
    Subdomain
    In-House development with
    

    external support if possible
    Generic
    Subdomain
    Outsourcing is an option
    Core
    (sub)Domain
    In-House development
    

    with Your best teams
    Key differentiator
    

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29. Domains & Subdomains
    Development Strategy
    Supporting
    Subdomain
    Customized Off The Shelf Software
    

    is an option
    Generic
    Subdomain
    Try to
    fi
    nd Off The Shelf solution
    
    
    Cost saving opportunities
    Core
    (sub)Domain
    Custom-made software
    
    
    High Cost & Quality
    Key differentiator
    

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30. From Problem to Solution
    Payment
    processor
    Invoicing
    Order
    Processing
    Shipping
    Authoring
    Plateforme
    Inventory
    Management
    Catalogue
    Publishing
    Proofreading
    Inventory E-commerce platform
    Authoring
    Publishing
    Authoring
    Plateform
    Publishing
    & Printing
    Inventory
    Management
    Shipping
    Payment
    Processor
    Catalogue
    Invoicing
    Order
    Processing
    Proofreading
    

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31. From Problem to Solution
    Inventory E-commerce platform
    Authoring
    Authoring
    Plateforme Publishing
    Catalogue
    Publishing
    Proofreading
    Authoring
    Plateform
    Publishing
    & Printing
    Inventory
    Management
    Shipping
    Payment
    Processor
    Catalogue
    Invoicing
    Order
    Processing
    Proofreading
    

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32. From Problem to Solution
    Business Domain & Architecture alignment
    Inventory E-commerce
    
    
    platform
    Authoring
    Authoring
    Plateforme Publishing
    Catalogue
    Publishing
    Proofreading
    These are your bounded contexts
    

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33. Inventory E-commerce
    
    
    platform
    Authoring
    Publishing
    Align your teams with your
    bounded context
    « Team assignments are the
    fi
    rst
    draft of the architecture »
    – Michael Nygard
    

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34. P
    Authoring
    Publishing
    E-commerce
    Stripe
    ShipMonk Shopify
    Context Mapping
    Relationship Hierarchy
    OHS
    OHS
    ACL
    OHS
    C/S
    

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35. Authoring
    Publishing
    E-commerce
    Specific Architecture style
    You don’t need one architectural style
    Beware of the CRUD
    ES
    CQRS
    CRUD ?
    Stripe
    ShipMonk Shopify
    

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36. Stripe
    Still no microservices
    Bounded Context ≠ Deployment units
    ShipMonk
    Authoring
    Publishing
    E-commerce
    Shopify
    Deployment Unit
    

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37. Deployment Unit
    Stripe
    Still no microservices
    Bounded Context ≠ Deployment units
    ShipMonk
    Authoring
    Publishing
    E-commerce
    Shopify
    Deployment Unit
    

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38. Domains are not immutable
    Understanding is a never-ending process
    Stripe
    ShipMonk
    Authoring
    Publishing
    E-commerce
    Shopify
    Printing
    

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39. www.lilobase.me
    DDD is all about
    Boundaries
    @lilobase
    

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40. Semantic Boundaries
    Between BC meaning are different
    Authoring Publishing
    Book
    Chapter
    Chapter
    They are not the same book
    What
    happens if
    the author
    revises his
    book?
    

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41. Semantic Boundaries
    Between BC meaning are different
    Chapter
    This is why you must start by understand
    strategically your domain
    Author
    Book
    Reviews
    Release
    Catalogue
    

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42. Semantic Boundaries
    Between BC meaning are different
    Authoring Publishing
    Book
    Chapter
    Chapter
    Book
    Chapter
    Chapter
    Inside a
    Bounded
    Context,
    

    Don’t
    

    Repeat
    

    Yourself
    Between
    Bounded
    Context,
    

    Write
    

    Everything
    

    Twice
    

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43. Don’t cross them
    Between BC meaning are different
    Authoring Publishing
    Author
    Reviews
    Author
    Book Book
    Release
    Never create relationships
    between entities from two BC
    

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44. Don’t cross them
    Between BC meaning are different
    Authoring Publishing
    Book Book
    Release
    Author
    Author
    Reviews
    This is exactly the same
    

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45. Don’t cross them
    Between BC meaning are different
    Authoring Publishing
    Book Book
    Release
    Author
    Author
    Reviews
    API API
    

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46. Same for Events
    Between BC meaning are different
    Authoring Publishing
    This is exactly the same
    Event
    

    Bus
    Book Book
    Release
    Author
    Author
    Reviews
    

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47. Same for Events
    Between BC meaning are different
    Authoring Publishing
    Event
    

    Bus
    Book Book
    Release
    Author
    Author
    Reviews
    Translator Translator
    

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48. Transactional Boundaries
    Protect your integrity
    Authoring
    Book
    Chapter
    Chapter
    Chapter
    Statistics
    Inside your
    bounded
    Context
    

    live
    

    Entities
    They are
    grouped in
    Aggregates
    

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49. Transactional Boundaries
    Protect your integrity
    Book
    Chapter
    Chapter
    Chapter
    Statistics
    They are
    retrieved
    and
    persisted
    

    as a whole
    Inside an
    aggregate,
    Entities
    

    share the
    same
    lifecycle
    

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50. Transactional Boundaries
    Protect your integrity
    Book
    Chapter
    Chapter
    Chapter
    Statistics
    Who
    ensures the
    aggregate
    integrity
    All
    interactions
    are done
    through the
    Aggregate
    Root
    Write a new chapter
    

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51. Transactional Boundaries
    Protect your integrity
    Book
    Chapter
    Chapter
    Chapter
    Statistics
    Write a new chapter
    Chapter
    Inconsistency
    

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52. Transactional Boundaries
    Protect your integrity
    Book
    Chapter
    Chapter
    Chapter
    Statistics
    But don’t
    put to much
    in it
    Author
    What
    happens if
    we delete
    the book ?
    They must share the same lifecycle
    

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53. Transactional Boundaries
    Protect your integrity
    Book
    Chapter
    Chapter
    Chapter
    Statistics
    Author
    reference
    Author
    Id
    

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54. Designing Boundaries
    Protect your domain
    Printing Team
    We need printing
    margin
    Book
    Chapter
    Chapter
    Chapter
    Release
    We need the
    colorimetric pro
    fi
    le
    Printing
    margin
    Colorimetric
    pro
    fi
    le
    API
    Publishing Team
    

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55. Designing Boundaries
    Protect your domain
    API
    We need printing
    margin
    Book
    Chapter
    Chapter
    Chapter
    Release
    We need the
    colorimetric pro
    fi
    le
    Printing
    margin
    Colorimetric
    pro
    fi
    le
    Domain Leakage
    Publishing Team Printing Team
    

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56. Designing Boundaries
    Protect your domain
    Publishing Team Printing Team
    Publishing
    API
    We need
    printing margin
    Book
    We need the
    colorimetric
    pro
    fi
    le
    Printing
    margin
    Colorimetric
    pro
    fi
    le
    Printing API
    We discovered the need
    

    for an ACL
    

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57. www.lilobase.me
    DDD is all about
    Behavior
    @lilobase
    

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58. CRUD don’t express behavior
    It blinds you from the business perspective
    UPDATE address
    Relocation Mistake correction
    

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59. CRUD don’t express behavior
    It blinds you from the business perspective
    Relocation Mistake correction
    

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60. Data oriented programming
    It obfuscates your code
    – Mathias Verraes
    $order->setStatus('paid');
    $order->setPaidAmount(120);
    $order->setPaidCurrency('EUR');
    $order->setCustomer($customer);
    

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61. Data oriented programming
    It obfuscates your code
    $money = new Money(120, new Currency(‘EUR'));
    $order->pay($customer, $money);
    – Mathias Verraes
    $customer->pay($order, $money);
    

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62. Data oriented programming
    It obfuscates your code
    – Mathias Verraes
    $customer->pay($order, $money);
    $order->setStatus('paid');
    $order->setPaidAmount(120);
    $order->setPaidCurrency('EUR');
    $order->setCustomer($customer);
    

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63. Task Based UI
    Your customer’s need isn’t to
    fi
    ll out forms
    

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64. Users don’t need to fill out forms
    

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65. Users don’t need to fill out forms
    

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66. www.lilobase.me
    DDD is all about
    Compassion
    @lilobase
    

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67. A A
    A
    Ubiquitous language
    Stakeholders & Team Alignement
    Dev Domain
    

    Expert
    Dev
    

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68. A A
    A
    not « just » a glossary
    Ubiquitous language
    Stakeholders & Team Alignement
    Dev Domain
    

    Expert
    Dev
    

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69. Ubiquitous language
    Each BC has its own
    Authoring Publishing
    A A
    

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70. Ubiquitous language
    Each BC has its own
    Authoring Publishing
    A A
    A A
    It is a common cause of
    miscommunication
    

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71. Pair Programing
    The best way to share a domain understanding
    Dev Domain
    

    Expert
    

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72. Know your users
    They might not be who you think they are
    Dev Domain
    

    Expert
    Product
    

    Owner
    Customer User
    

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73. Know your users
    They might not be who you think they are
    Dev Domain
    

    Expert
    Product
    

    Owner
    Customer User
    He has the last word regarding
    domain implementation
    

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74. Know your users
    They might not be who you think they are
    Dev Domain
    

    Expert
    Product
    

    Owner
    Customer User
    Prioritize development &
    formalize users’ feedback
    

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75. Know your users
    They might not be who you think they are
    Dev Domain
    

    Expert
    Product
    

    Owner
    Customer User
    Power of Life and Death over the
    project
    

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76. Know your users
    They might not be who you think they are
    Dev Domain
    

    Expert
    Product
    

    Owner
    Customer User
    Too often forgotten
    

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77. Know your users
    They might not be who you think they are
    Dev Domain
    

    Expert
    Product
    

    Owner
    Customer User
    Maybe you could spend a day per
    month working with them ?
    

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78. Know your users
    They might not be who you think they are
    Dev Domain
    

    Expert
    Product
    

    Owner
    Customer User
    They design the software
    speci
    fi
    cation
    

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79. Know your users
    They might not be who you think they are
    Dev Domain
    

    Expert
    Product
    

    Owner
    Customer User
    What he understood goes
    

    into production
    

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80. www.lilobase.me
    DDD is for every
    Projects
    @lilobase
    

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81. “A loosely coupled software
    architecture and org
    structure to match” is a key
    predictor of:
    
    
    • Continuous Delivery
    Performance
    
    
    • Ability to scale
    organization and increase
    performance linearly
    This is what DDD is All About !
    — Michael Plöd (@bitboss)
    

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82. www.lilobase.me @lilobase
    sundayapp.com
    Thanks
    

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