7 Years of DDD: Tackling Complexity in Marketing Systems

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7 YEARS OF DDD: TACKLING COMPLEXITY  IN LARGE SCALE MARKETING SYSTEMS

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Vladik Khononov IAF Malam Team MSN-IL Cellcom Internovus Twitter: @vladikk    Blog: vladikk.com

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Vladik Khononov IAF Malam Team MSN-IL Cellcom Internovus Twitter: @vladikk    Blog: vladikk.com

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AGENDA

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PART 1  5 BOUNDED CONTEXTS PART 2 PRACTICAL ADVICE

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YAY!!!

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Your Product Marketing  Strategy Creatives Campaigns Sales  Agents Optimization Profits

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THE FIRST BOUNDED CONTEXT 01

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VER 1.0 Media Buying Creatives Catalog Campaign Management

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Very nice!

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Aggregates everywhere!!!

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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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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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Domain Model Service / Application Layer Presentation Infrastructure Anemic! Behaviour

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

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UBIQUITOUS LANGUAGE

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Domain Expert Software Developer Has no experience in online marketing Nice people!

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

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Ubiquitous Language Anemic Domain Model

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Leads Sales Agents Ads

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

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Lead qualification Agent qualification Agents’ commissions

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THE CRM BOUNDED CONTEXT 02

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Ubiquitous Language Anemic Domain Model

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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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Domain Expert Software Developer …. Lead …. …. Campaign…

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BOUNDED CONTEXTS PROTECT THE LANGUAGE AGGREGATES PROTECT CONSISTENCY OF DATA

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

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

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Stored procedures???

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

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

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Ubiquitous Language Domain Model Bounded Contexts Protect w/ Implement as

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Ubiquitous Language Domain Model Bounded Contexts Protect w/ Implement as …Dude, where are Sub-Domains?

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

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THE CRUNCHERS BOUNDED CONTEXT 03

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Marketing CRM Analysis Customer Events Marketing CRM

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Marketing CRM Analysis Customer Events Event Crunchers

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

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Layered Architecture Transaction Script Worked …. for a while

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Customer Events Event Crunchers Marketing CRM Analysis Flag Flag Calculated fields

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Marketing CRM Analysis Customer Events Event Crunchers

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Customer Events Event Crunchers (BBOM) CRM Marketing Analysis

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Customer Events Event Crunchers (Event Sourced) CRM Marketing Analysis

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THE BONUSES BOUNDED CONTEXT 04

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Sales Commissions Reports

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

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Active Record Service / Application Layer Presentation Infrastructure

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

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

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

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Event Sourced Domain Model Service / Application Layer Presentation Infrastructure Event Sourced Domain Model Service / Application Layer Presentation Infrastructure Event Crunchers Bonuses Ubiquitous Language

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

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THE MARKETING HUB BOUNDED CONTEXT 05

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Leads Marketing Hub Client Client Client

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Competitive advantage? - Yes => Core Domain

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Event Sourced Domain Model CQRS Microservices

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Micro  Service Micro  Service Micro  Service Micro  Service

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Aggregate Aggregate Aggregate Aggregate

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Aggregate Aggregate Aggregate Aggregate Event Sourced  Aggregate

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Aggregate Aggregate Aggregate Aggregate Event Sourced  Aggregate

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Event Sourced Domain Model CQRS Microservices

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Aggregate Aggregate Aggregate Aggregate Event Sourced  Aggregate

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TECHNICAL COMPLEXITY BUSINESS COMPLEXITY >

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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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UBIQUITOUS LANGUAGE 01

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Ubiquitous Language: The Core Domain of Domain-Driven Design

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UBIQUITOUS LANGUAGE DOCUMENTS TESTS JIRA >

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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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Invest in the Ubiquitous Language early on.

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Cheap!

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You don’t need a budget for a Ubiquitous Language

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DOMAIN TYPES 02

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Core Supporting Generic

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

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

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

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

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Less waste Dialog with the business IMPLEMENTATION DESIGN ➤ DOMAIN TYPE

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

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

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IMPLEMENTATION STRATEGIES 03

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How to Model the Business Logic? Transaction Script Active Record Domain Model Event Sourced Domain Model

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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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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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Transaction Script Active Record Domain Model Event Sourced Domain Model

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

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Transaction Script Active Record Domain Model Event Sourced Domain Model

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CQRS 04

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Event Sourcing ➤ CQRS

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EVENT SOURCING A WAY OF MODELING BUSINESS DOMAINS CQRS ARCHITECTURAL PATTERN FOR REPRESENTING THE SAME DATA IN DIFFERENT MODELS

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

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05 BOUNDED CONTEXTS

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Bonuses Event Crunchers DOMAIN-BASED BOUNDARIES

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AGGREGATE-BASED BOUNDARIES Aggregate Aggregate Aggregate Aggregate

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L e a d SUICIDAL BOUNDARIES

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

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

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START WITH BIGGER BOUNDARIES DECOMPOSE LATER, AS YOU GAIN KNOWLEDGE

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THE LESS YOU KNOW ABOUT THE DOMAIN - THE WIDER THE INITIAL BOUNDARIES ARE

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Aggregate Aggregate Aggregate Aggregate Event Sourced  Aggregate

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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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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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START WITH BIGGER BOUNDARIES DECOMPOSE AS YOU GAIN DOMAIN KNOWLEDGE

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1. Ubiquitous Language is not optional 2. Domain Types change. Embrace these changes 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. Start with bigger boundaries, and divide as you gain domain knowledge

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07 SUMMARY

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Ubiquitous Language Bounded Contexts Protect by  decomposing to Design  Implementation Core Supporting Generic Domain Model AR / TS Adopt Confirm w/  Business

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Ubiquitous Language Bounded Contexts Protect by  decomposing to Design  Implementation Core Supporting Generic Domain Model AR / TS Adopt Confirm w/  Business

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Ubiquitous Language Bounded Contexts Protect by  decomposing to Design  Implementation Core Supporting Generic Domain Model AR / TS Adopt Confirm w/  Business

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Ubiquitous Language Bounded Contexts Protect by  decomposing to Design  Implementation Core Supporting Generic Domain Model AR / TS Adopt Confirm w/  Business

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Ubiquitous Language Bounded Contexts Protect by  decomposing to Design  Implementation Core Supporting Generic Domain Model AR / TS Adopt Confirm w/  Business

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

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Ubiquitous Language Bounded Contexts Protect by  decomposing to Design  Implementation Core Supporting Generic Domain Model AR / TS Adopt Confirm w/  Business Ubiquitous Language Everywhere!!!