7 Years of Domain-Driven Design

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vladikk 7 YEARS OF DDD or Tackling Complexity in  Large Scale Marketing Systems

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YAY!!!

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@vladikk vladikk.com Internovus

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vladikk PART 2   5 PRACTICAL ADVICES PART 1  5 BOUNDED CONTEXTS

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vladikk Your Product Marketing  Strategy Creatives Campaigns Sales  Agents Optimization Profits

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vladikk THE FIRST BOUNDED CONTEXT 01

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vladikk Media Buying Creatives Catalog Campaign Management VER 1.0

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vladikk

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vladikk

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Very nice!!!1

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vladikk Aggregates everywhere!!!

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vladikk Aggregates everywhere!!! Creative Agency Advertiser Publisher Website Placement Ad Zone Ad Type Target Market Group Zone Type Funnel Contract Budget Unit Campaign

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vladikk The Bounded Context Creative Agency Advertiser Publisher Website Placement Ad Zone Ad Type Target Market Group Zone Type Funnel Contract Budget Unit Audience

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vladikk Domain Model Service / Application Layer Presentation Infrastructure Anemic! Behaviour

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vladikk Imperfect architecture “QA is for cowards” BUT IT WORKED!

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vladikk UBIQUITOUS LANGUAGE

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vladikk Domain Experts Software Developers No experience in online marketing Nice people!

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vladikk Smooth communication Strong grasp of the business domain Working software Aggressive time to market

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vladikk Ubiquitous Language Anemic Domain Model

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vladikk Leads Sales Agents Ads

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vladikk Leads CRM Categorize Desk Desk Desk Sales Agents Sales Agents Sales Agents

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Leads CRM Categorize Desk Desk Desk Sales Agents Sales Agents Sales Agents Clients’ Systems

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vladikk

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vladikk Lead qualification Agent qualification Agents’ commissions

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vladikk THE CRM BOUNDED CONTEXT 02

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vladikk Ubiquitous Language Anemic Domain Model

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vladikk Creative Agency Publisher Website Advertiser Ad Zone Ad Type Target Market Group Zone Type Funnel Contract Budget Unit Audience Group Desk Qualification Assessment Organization Unit Assignment Rank Message On-site Activity Placement Visit Brand Marketing Lead CRM Lead Marketing Campaign CRM Campaign

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vladikk Domain Experts Software Developers …. Lead …. …. Campaign…

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vladikk

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vladikk BOUNDED CONTEXTS PROTECT THE LANGUAGE AGGREGATES PROTECT CONSISTENCY OF DATA

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vladikk Creative Agency Publisher Website Advertiser Ad Zone Ad Type Target Market Group Zone Type Funnel Contract Budget Unit Audience Placement Visit Lead Campaign Marketing Group Desk Qualification Assessment Organization Unit Assignment Rank Message On-site Activity Brand Lead Campaign CRM

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vladikk Aggregates will:  • Protect transactional boundaries  • Encompass business logic and invariants Domain Service / Application Layer Presentation Infrastructure

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vladikk Aggregates will:  • Protect transactional boundaries  • Encompass business logic and invariants Domain Service / Application Layer Presentation Infrastructure Domain Service / Application Layer

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vladikk

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vladikk Stored procedures???

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vladikk Group Desk Qualification Assessment Organization Unit Assignment Rank Message On-site Activity Brand Lead Campaign Lead

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L e a d CRM Team DBA Team

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vladikk Inconsistent models No shared understanding Duplication of knowledge Went out of sync quickly NIGHTMARE

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vladikk Wasn’t delivered on time Production issues Data corruption Thrown away and reimplemented

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vladikk Ubiquitous Language Domain Model Bounded Contexts Protect w/ Implement as

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Not all of a large system will be well designed “ Eric Evans

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vladikk THE CRUNCHERS BOUNDED CONTEXT 03

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vladikk Marketing CRM Analysis Customer Events Marketing CRM

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vladikk Marketing CRM Analysis Customer Events Event Crunchers

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vladikk Competitive advantage? - No Off-the-shelve solution? - No => Supporting sub-domain

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vladikk Layered Architecture Transaction Script Worked …. for a while

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vladikk Customer Events Event Crunchers Marketing CRM Analysis Flag Flag Calculated fields

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vladikk

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vladikk Marketing CRM Analysis Customer Events Event Crunchers

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vladikk Customer Events Event Crunchers (BBOM) CRM Marketing Analysis

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vladikk Customer Events Event Crunchers (Event Sourced) CRM Marketing Analysis

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vladikk THE BONUSES BOUNDED CONTEXT 04

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vladikk Sales Commissions Reports

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vladikk Competitive advantage? - No Off-the-shelve solution? - No => Supporting sub-domain

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vladikk Active Record Service / Application Layer Presentation Infrastructure

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vladikk Sales Commissions Reports Let’s try different percentages What if the percentage could be a function of a price? No, what if the percentage is a function of number of sales? No, no, the percentage will be a function both of number of sales and sale amount And another upgrade if there are more than Y sales per week! But we will upgrade the percentage if there are more than X sales per month!

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vladikk Active Record Service / Application Layer Presentation Infrastructure BIG BALL OF MUD

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vladikk Event Sourced Domain Model Service / Application Layer Presentation Infrastructure BIG BALL OF MUD

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vladikk Active Record Service / Application Layer Presentation Infrastructure Transaction Script Service / Application Layer Presentation Infrastructure Event Crunchers Bonuses Ubiquitous Language

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vladikk Ubiquitous Language Core Bounded Contexts Protect by  decomposing to Identify Domains Domain Model Supporting Generic AR / TS Adopt Implement as

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vladikk THE MARKETING HUB BOUNDED CONTEXT 05

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vladikk Leads Marketing Hub Client Client Client

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vladikk Competitive advantage? - Yes => Core Domain

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vladikk Event Sourced Domain Model CQRS Microservices

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vladikk Micro  Service Micro  Service Micro  Service Micro  Service

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vladikk Aggregate Aggregate Aggregate Aggregate

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vladikk Aggregate Aggregate Aggregate Aggregate Event Sourced  Aggregate

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vladikk Aggregate Aggregate Aggregate Aggregate Event Sourced  Aggregate

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vladikk Event Sourced Domain Model CQRS Microservices

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vladikk Aggregate Aggregate Aggregate Aggregate Event Sourced  Aggregate

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vladikk TECHNICAL COMPLEXITY BUSINESS COMPLEXITY >

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vladikk Aggregate Aggregate Aggregate Aggregate Event Sourced  Aggregate

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Marketing Bonuses U D CRM U D Marketing  Hub U U D D Event Crunchers U D U D

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WHAT  WE HAVE L E A R N E D

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vladikk UBIQUITOUS LANGUAGE 01

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vladikk UBIQUITOUS LANGUAGE THE CORE DOMAIN OF DOMAIN-DRIVEN DESIGN

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vladikk Marketing Ubiquitous Language Business goals achieved CRM Ubiquitous Language Production issues Long and painful refactoring Event Crunchers Ubiquitous Language Big ball of mud Bonuses Ubiquitous Language Refactored in time

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vladikk Invest in the Ubiquitous Language early on

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vladikk Cheap!

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vladikk DOMAIN TYPES 02

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vladikk Core Supporting Generic

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vladikk Generic Domain Adopt / Buy Supporting Domain Active Record / Transaction Script Core Domain Domain Model / Event Sourcing

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vladikk COMPANIES CHANGE, EVOLVE, REINVENT THEMSELVES DOMAINS' TYPES CHANGE ACCORDINGLY

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vladikk SUPPORTING ➤ CORE • Event Crunchers • Bonuses SUPPORTING ➤ GENERIC • Creative Catalog CORE ➤ GENERIC • Lead Evaluation System CORE ➤ SUPPORTING • Marketing Hub GENERIC ➤ CORE • AWS

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vladikk Generic Domain Adopt / Buy Supporting Domain Active Record / Transaction Script Core Domain Domain Model / Event Sourcing

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vladikk Generic Domain Adopt / Buy Supporting Domain Active Record / Transaction Script Core Domain Domain Model / Event Sourcing

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vladikk Less waste Dialog with the business IMPLEMENTATION DESIGN ➤ DOMAIN TYPE

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vladikk • Questionable competitive edge? • Accidental “business” complexity? • Unexpected competitive edge? BUSINESS COMPLEXITY ≠ DOMAIN TYPE?

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vladikk Generic Domain Adopt / Buy Supporting Domain Active Record / Transaction Script Core Domain Domain Model / Event Sourcing IMPLEMENTATION DESIGN ➤ DOMAIN TYPE

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vladikk IMPLEMENTATION STRATEGIES 03

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vladikk How to Model the Business Logic?

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vladikk How to Model the Business Logic? Transaction Script (PoEAA) Active Record (PoEAA) Domain Model (PoEAA + DDD) Event Sourced Domain Model

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vladikk MONEY? DEEP ANALYTICS? AUDIT LOG? Event Sourced Domain Model COMPLEX BUSINESS LOGIC? Domain Model COMPLEX DATA STRUCTURES? Active Record SIMPLE LOGIC, SIMPLE DATA STRUCTURES? Transaction Script

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vladikk MAPPING ARCHITECTURAL PATTERNS Event Sourced Domain Model ➤ CQRS Domain Model ➤ Hexagonal Architecture Active Record ➤ Layered Architecture Transaction Script ➤ “Keep it simple” Architecture

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vladikk Transaction Script Active Record Domain Model Event Sourced Domain Model

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vladikk PAIN? BUSINESS CHANGED? DOMAIN TYPE CHANGED? REVISE IMPLEMENTATION STRATEGY? ➤

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vladikk Transaction Script Active Record Domain Model Event Sourced Domain Model

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vladikk CQRS 04

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vladikk Event Sourcing ➤ CQRS

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vladikk EVENT SOURCING BUSINESS DOMAIN MODELING PATTERN CQRS ARCHITECTURAL PATTERN FOR REPRESENTING DATA IN DIFFERENT PERSISTENT MODELS

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vladikk Transaction Script Active Record Domain Model } Can benefit from CQRS and State-Based Projections

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vladikk RDBMS Search index Files  storage Projection  Engine Projected  Model Projected  Model Changes Application Query Query Commit

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vladikk COMMAND QUERY   RESPONSIBILITY SEGREGATION?

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vladikk Did command succeed or fail? If failed - why? What are the outcomes? } Can be delivered asynchronously through queries … but why?

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vladikk Write  Model Projection Projection Projection  Engine Projected  Model Projected  Model Changes Application Client Command  Execution Result Query

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vladikk 05 BOUNDED CONTEXTS

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vladikk Bonuses Event Crunchers DOMAIN-BASED BOUNDARIES

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vladikk AGGREGATE-BASED BOUNDARIES Aggregate Aggregate Aggregate Aggregate

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vladikk L e a d SUICIDAL BOUNDARIES

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vladikk

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vladikk BOUNDED CONTEXTS ARE NOT MICROSERVICES

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vladikk BOUNDED CONTEXTS PROTECT INTEGRITY OF A UBIQUITOUS LANGUAGE

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vladikk MICROSERVICES DECOMPOSITION OF A SYSTEM INTO LOOSELY COUPLED COMPONENTS BOUNDED CONTEXTS PROTECT INTEGRITY OF A UBIQUITOUS LANGUAGE

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vladikk Micro  Service Micro  Service Micro  Service Micro  Service

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Finding service boundaries is really damn hard… There is no flowchart! “ Udi Dahan

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vladikk THERE ARE GOING TO BE MISTAKES ACCEPT IT AND DON’T MAKE FATAL ONES

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vladikk THE LESS YOU KNOW ABOUT THE DOMAIN THE WIDER THE INITIAL BOUNDARIES START WITH BIGGER BOUNDARIES DECOMPOSE LATER, AS YOU GAIN KNOWLEDGE

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vladikk Aggregate Aggregate Aggregate Aggregate Event Sourced  Aggregate

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vladikk Marketing Creative Agency Publisher Website Advertiser Ad Zone Ad Type Target Market Group Zone Type Funnel Contract Budget Unit Audience Placement Visit Lead Campaign

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vladikk Campaigns Creative Ad Type Agency Publisher Website Zone Type Contract Budget Unit Impression Visit Lead Advertiser Target Market Funnel Audience Placement Campaign Creative Catalog Publishers Events

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vladikk START WITH BIGGER BOUNDARIES DECOMPOSE AS YOU GAIN DOMAIN KNOWLEDGE

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vladikk 1. Ubiquitous Language is not optional 2. Domain Types change. Embrace these changes to achieve resilient design 3. Learn the ins and outs of the four patterns of modeling business logic 4. Use CQRS to represent the same data in multiple models 5. Bounded Contexts are not Microservices. Always start with bigger boundaries, but decompose further as you gain domain knowledge

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