Understanding Bounded Contexts in Microservices and Domain-Driven Design
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1) The document discusses the importance of bounded contexts in software design, particularly for microservices. It notes that bounded contexts allow separating a domain into sub-domains or contexts that each have their own model. 2) The document uses the example of how Amazon might model a book for different purposes like catalog, shipping, etc. It argues that having separate models per context avoids duplication and allows independent evolution of the sub-domains. 3) It provides some heuristics for identifying bounded contexts, such as by sub-domain, common changes, mental consensus of stakeholders, and clustering of functions and data. The document emphasizes that bounded contexts promote loose coupling and independence between contexts.
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Understanding Bounded Contexts in Microservices and Domain-Driven Design
- 2. You may not know yet…
- 5. You need Bounded Contexts absolutely!
- 8. Passionate developer Deliberate Designer PARIS Since 1999 @cyriux Cyrille Martraire
- 9. Paris Software Crafters Community since 2011 http://www.meetup.com/paris-software-craftsmanship/
- 12. ”The DDD guy from Paris”
- 14. We heard about modelling a domain…
- 15. Let’s practice!
- 16. What are pants? Give a clear definition 2mn
- 17. Was it easy?
- 18. Did you hesitate between different definitions?
- 19. ”To cover the ass”
- 21. ”To cover the legs”
- 25. •Decency: Cover the ass •Protection: Cover the legs •Status: Famous brand •Self-Expression: The way you wear it •Fashion: Leg cuts •…
- 28. CONTEXTS
- 29. Which model is right?
- 30. The ONE you need for each purpose!
- 31. The ONE you need for each Context!
- 32. “At Amazon, what a book is for you?” •Catalog: Picture, title, authors, rating, format (ebook or paper), category •Recommandation: List of books often bought together with it •Shipping: Dimensions, weight, international restrictions due to content •Shopping cart: Price, discount eligible •Customer review: List of (rating, review, review rating) •Book Search: title, isbn, authors •Search Inside!: full-text content, copyright- dealing policy
- 33. One Book. Many Views. Book To Read Buyable Catalog Shopping Cart Searchable Search Billable Billing Recommendable Recommandation Priceable Pricing Shippable Shipping
- 34. “At Amazon, what a book is for you?” •Catalog: Picture, title, authors, rating, format (ebook or paper), category •Recommandation: List of books often bought together with it •Shipping: Dimensions, weight, international restrictions due to content •Shopping cart: Price, discount eligible •Customer review: List of (rating, review, review rating) •Book Search: title, isbn, authors •Search Inside!: full-text content, copyright- dealing policy 1 context 1 model
- 35. Different perspectives MY catalogue/book is not YOUR shipping/book
- 37. in isolation
- 38. ISOLATION FTW!
- 40. BOUNDED Contexts
- 41. BOUNDED Contexts
- 42. BOUNDED Contexts
- 45. •Sales -> Customer •Shipping -> Recipient •Billing -> Account •Marketing -> Segment, Audience Linguistic Contexts
- 46. •Customer -> Sales •Recipient -> Shipping •Account -> Billing •Segment, Audience -> Marketing Linguistic Contexts
- 47. Fraud Détection Payment Gift Cards n mpany ting Review Shopping Cart Payment Event Anomaly Agent Transaction Transaction Status Account Basket Items Recent Baskets
- 48. Fraud Détection Payment Gift Cards n mpany ting Review Shopping Cart Payment Event Anomaly Agent Transaction Transaction Status Account Basket Items Recent Baskets
- 51. Different (Sub)Domains Different Bounded Context HEURISTICS
- 52. Different (Sub)Domains Different Bounded Context HEURISTICS 98% of the time
- 53. Different (Sub)Domains Different Bounded Context HEURISTICS 98% of the time (precisely LOL)
- 55. “At Amazon, what sub-domains?” •Catalog •Recommandation •Shipping •Billing •Shopping cart •Customer review •Book Search •Search Inside!
- 57. How do we identify Bounded Contexts? 57
- 58. 58 How do we identify Sub Domains?
- 59. We want IT alignment blabla…
- 60. We want IT alignment blabla…
- 61. I know how to do that! Once you know DDD…
- 69. Different (Sub)Domains Different Evolution and Different Feature / Change Requests HEURISTICS
- 70. Strategic Design (aka in the long run) 70
- 72. Hey! Companies have a different billing address!
- 73. I know: let’s add it with a flag!
- 75. Customer addressLine zipcode city has2AddressesFlag addressLine2 zipcode2 city2 If (! has2AddressesFlag) billing address line = … billing zip code = billing city = else billing address line = … billing zip code = billing city =
- 76. Customer addressLine zipcode city has2AddressesFlag addressLine2 zipcode2 city2 If (! has2AddressesFlag) billing address line = … billing zip code = billing city = else billing address line = … billing zip code = billing city = Everywhere
- 78. Split by business domains 78
- 86. Customer addressLine zipcode city date amount user Account addressLine zipcode city Recipient + + Default value: billing address = shipping address
- 91. Isolation + Redundancy DRY+ Coupling
- 92. DRY == Coupling Bounded Contexts: We decide to reduce coupling at the cost of some redundancy 92
- 93. Evolve differently in the long term 93
- 99. Different Bounded Context Different MODELs of the same thing •Catalog: RECORD (Picture, title, authors, rating, format (ebook or paper), category) •Recommandation: CLUSTER (List of ID’s often bought together with this ID) HEURISTICS Book:
- 100. Different Company Departments Different Bounded Contexts (often, but never consistently) HEURISTICS
- 101. Sub-Domains Names • Often end in ”-ing” or ”-tion” • Because purpose verbs made into nouns HEURISTICS
- 102. Mental Consensus of Everyone Involved • Directors by departments (Marketing, Sales, Operations, Customer Support…) • Interviews people and listen to their purpose & language PRACTICE
- 103. Pre-NegotiationListing) B2BOrdering Fraud Détection Payment Sourcing Distribution Rates Grid RealTime Prices Gift Cards Content & Comparators Sales Promotion Acquisition TV Campaigns Online Ads Company Rating Product Reviews Shopping Cart Catalogue Search Categories Tags PartnershipsSecondary Listing Internal Purchasing Rates CrossSales Navigation SEO Marketing
- 105. Different (Sub)Domains Mostly Independent Clusters of (Functions + Data) HEURISTICS
- 106. High Cohesion Low Coupling Within a ”CLUSTER” Customer ———— ShippingAddress BillingAddress OrderHistory PaymentStats AddressValidationStatus … ValidateOrder EmitInvoice ValidateAddress ConfirmOrder EstimateShippingCost DisplayOrderHistory …
- 107. High Cohesion Low Coupling Within a Bounded Context Customer ———— ShippingAddress BillingAddress OrderHistory PaymentStats AddressValidationStatus … ValidateOrder EmitInvoice ValidateAddress ConfirmOrder EstimateShippingCost DisplayOrderHistory …
- 109. Search
- 110. Reporting
- 111. e-commerce Bounded Contexts • SEO, Traffic Acquisition • Marketing & Targeting • PIM (Product Identification Management) • Catalogue • Categorization • Search • Recommendation • Pricing, Promotions • Basket • Discount, Loyalties • Shipping Cost Estimation • Payment • (Fraud Detection) • Order Management • Billing • Stock / Overbooking • Shipping • Return • CRM
- 112. Wait until the sub-domains are stable and obvious HEURISTICS
- 113. Different Bounded Contexts Different Implementation Style PRACTICE
- 116. in Closing
- 120. Invest into DDD / Strategic Design
- 121. A Differentiating skills for developers & architects today!