2020-06-27 DDD Taiwan Community Microservices Bounded Context and everything in Between

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© 2020, Domain Driven Design Taiwan Community Kim Kao, Co-Organizer Domain Driven Design Taiwan Community 27 June, 2020 Microservices Bounded Context And everything in Between @YiKaiKao Kim Kao @Vladikk

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© 2020, Domain Driven Design Taiwan Community Kim, Kao (高翊凱) • A father of 2 • Love Softball / Baseball • Passionate facilitator • Domain Driven Design Taiwan Community Co-Organizer • Solutions Architect @AWS – Big Serverless Fan !!!

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© 2020, Domain Driven Design Taiwan Community Bounded Contexts Marketing Sales Funnel Campaign Placement Landing Page Agency Insertion Order Lead Contact CDR Conversion Desk Campaign Proposition Message Lead

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© 2020, Domain Driven Design Taiwan Community Marketing Sales Billing Creative Catalog Campaign Management Ads Optimization Identity & Access Contracts Telephony CRM Sales Optimization Commissions Desks Identity & Access

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© 2020, Domain Driven Design Taiwan Community Business Domain: Customer Acquisition Bounded Context: Marketing Bounded Context: Sales SubDomain: Creative Catalog SubDomain: Campaigns Mgt SubDomain: Ads Optimization SubDomain: Contracts Mgt SubDomain: CRM SubDomain: Sales Optimization SubDomain: Commissions SubDomain: Desk Mgt

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© 2020, Domain Driven Design Taiwan Community Decomposition Strategy #2: Subdomains Campaign Management service Content Catalog Service Desk Management Service CRM Service Users Service Billing Service

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© 2020, Domain Driven Design Taiwan Community Marketing Billing Creative Catalog Campaign Management Ads Optimization Identity & Access Contracts Campaign Management Campaign Placement Funnel Banner Website Asset Target Market Landing Page

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© 2020, Domain Driven Design Taiwan Community Marketing Support Sales Lead Lead Identity & Access Campaign Mgt Optimization Contracts Desks Telephony Billing Creative Catalog CRM Commissions Optimization

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© 2020, Domain Driven Design Taiwan Community Service “A service is a unit of functionality exposed to the world” – Juval Lowy “A mechanism to enable access to one or more capabilities, where the access is provided using a prescribed interface” - OASIS

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© 2020, Domain Driven Design Taiwan Community Microservice = Microinterface Reducing coupling between services Limits reasons for change Easier to understand Better fault isolation More autonomy between services

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© 2020, Domain Driven Design Taiwan Community “Global complexity … the complexity of the overall structure of a program or system. i.e, the degree of association or interdependence Among the major pieces of a program” Glenford J. Myers - 1978 Composite / Structured Design

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© 2020, Domain Driven Design Taiwan Community When you design a system…, then if the features can be break into … loosely bound groups of relatively closely bound features, then that division is a good thing to be mad a part of the design. This is just good engineering. Tim Berners-Lee Principles of design, 1998

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© 2020, Domain Driven Design Taiwan Community Its is not only necessary to make sure your own system is designed to be made of modular parts. It is also necessary to realize that your own system… should always be designed to be a part of another larger system. Tim Berners-Lee Principles of design, 1998

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© 2020, Domain Driven Design Taiwan Community A major part of this paper will be concerned with the question of how good modularity can be achieved, that is, how modules can be chosen to as to minimize the connections between them. Barbara Liskov A design methodology for reliable software systems, 1972

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© 2020, Domain Driven Design Taiwan Community A microservice is a service with a micro interface. The threshold upon which a system can be decomposed Into microservices is defined by the use cases of the System that the microservices are a part of.

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© 2020, Domain Driven Design Taiwan Community Core Subdomains Inventing something new Optimizing existing practices Competitive advantage Complex business logic Change often Services : Campaign, Ad Optimization, CRM, Sales, Commissions

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© 2020, Domain Driven Design Taiwan Community Supporting Subdomains No competitive advantage Support the Core Subdomains Can’t be bought / adopted Simple bussiness logic Services : Creative Catalog, Contracts, Desks

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© 2020, Domain Driven Design Taiwan Community Heuristic #6: Evaluate Consistency Requirements Eventual Consistency? – Two Services, async communication Method A Service A Method B Service B Async communication

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© 2020, Domain Driven Design Taiwan Community Heuristic #6: Evaluate Consistency Requirements Concurrency control? – Same Service Read last write? – Two services, sync communication Eventual consistency? – Two services, async communication

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© 2020, Domain Driven Design Taiwan Community Heuristic #7: Public / Private Events Service emailChanged phoneNumberChanged addressChanged contactDetailChanged Private event types (Implementation details) public event types (public interface)

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© 2020, Domain Driven Design Taiwan Community Wrap it up • A service is a unit of functionality exposed to the world through its public interface • A microservice is a service with micro interface • The “Micro-interface” is relative to the use cases of the system that the service is a part of

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© 2020, Domain Driven Design Taiwan Community Wrap it up • Heuristic #1: Always decompose to Bounded Contexts • Heuristis #2: Don’t go further, unless you have to • Heuristic #3: Buy/Adopt generic subdomains • Heuristic #4: Core subdomains – don’t rush • Heuristic #5: Supporting subdomains can be decomposed ear • Heuristic #6: Evaluate Consistency Requirements • Heuristic #7: Private / Public Events • Heuristic #8: Explicit Define Events • Heuristic #9: Evaluate Reasons for Change • Heuristic #10: Evaluate Services’ “Doors”