SlideShare a Scribd company logo

From DDD to CQRS

•
•
Dennis Traub
Dennis Traub

Presented at dnug-bern.ch on May 19th, 2013 by Dennis Traub

Technology
1 of 103
From DDD to CQRS presented by Dennis Traub .NET Usergroup Bern - 19. März 2013 Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Who‘s that guy? Dennis Traub Founder, Owner, CEO, Single Employee of D. Traub Software Development Consultancy Consultant, developer, trainer, speaker 39 years old Married, father of one 20+ years in software development Hire me at mail@dennistraub.de @dtraub Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
AGENDA DDD Recap CQRS Break Step by Step the strategic patterns probably simpler than you think! towards CQRS 1 2 3 4 5 6 „Best Practice“ Domain Events End what we call an Architecture are first class citizens Questions & Answers Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
AGENDA DDD Recap CQRS Step by Step the strategic patterns probably simpler than you think! towards CQRS 1 2 3 4 5 6 „Best Practice“ Domain Events End what we call an Architecture are first class citizens Questions & Answers Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
The „Blue Book“ by Eric Evans Image Placeholder Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Domain-Driven Design Domain Service Value Object Aggregate Specification The well- known Reposit ory Patterns Entity Factory And so on . . Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Domain-Driven Design Ubiquit ous Language Core Domain Domain Expert Bounded Context The important Domain Model Patterns (Generic) Subdomains Context Map And so on . . Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
don‘t build one big model that works for everyone Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
the tactical Building Blocks we don‘t use DDD when there is no value in formalizing the problem Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
we only use DDD in parts where we get a competitive advantage Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
we focus our effort and resources on the most important subdomain Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
a.k.a. The Core Domain Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
AGENDA DDD Recap CQRS Step by Step the strategic patterns probably simpler than you think! towards CQRS 1 2 3 4 5 6 „Best Practice“ Domain Events End what we call an Architecture are first class citizens Questions & Answers Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Presentation Layer Application Services Domain / Business Model / BLL DAL / O/R-Mapper Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Pros of the „Best Practice Architecture“ 1 Easy to build 2 Accepted by management 3 Well-know throughall all seniority levels 4 We know ist limitiations Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Cons of the „Best Practice Architecture“ 1 Limited scalability 2 Loss of intent 3 Lazy loading, locking, race conditions, … 4 Few classes do way too much stuff Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
And: If the model is basically CRUD where does Business Logic live? Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Domain Model Responsibilities 1 Business Logic 6 Aggregation 2 Validation 7 Presentation 3 Structure 8 Persistence 4 Projection 9 Processes 5 Associations 10 Lazy / Eager Loading Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
the S in SOLID Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Single Responsibility Principle just because we can doesn‘t mean we should Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
why do we try to build One Model to Rule Them All? Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
reading and writing are completely different from eachother Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Sometimes it‘s cheaper to do two things than dealing with the trade-offs Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
AGENDA DDD Recap CQRS Step by Step the strategic patterns probably simpler than you think! towards CQRS 1 2 3 4 5 6 „Best Practice“ Domain Events End what we call an Architecture are first class citizens Questions & Answers Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Command Query Separation Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Command Query Separation (CQS) „Every method should either be a command that performs an action or a query that returns data to the caller“ -- Dr. Bertrand Meyer Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Command Query Separation (CQS) in other words: Asking a question should not change the answer Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Command/Query Responsability Segregation Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
CQS on an Architectural Level Queries Commands Project Details Project List Project Data Store Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Queries and Projection (Read) Show something Thin Read Layer Data Store Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Thin Read Layer Concerns: 1 Filtering, Scope 2 Data Presentation Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Thin Read Layer Attributes: 1 Data-Oriented 2 Indexable 3 Can be denormalized and distributed for fast access 4 Only Structure Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Behavior and Modification (Write) Do something Command Handler Domain Model O/R-Mapper Data Store Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Domain Model Concerns: 1 Business Logic 2 Validation Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Domain Model Attributes: 1 Normalized 2 Transactional 3 Object-Oriented 4 Persistence Ignorant 5 Only Behavior Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Commands Refactor Application Service Calls to Objects 1 Serializable 2 Can be enveloped 3 Can be intercepted 4 Can be enriched 5 Communicate intent Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Command Handlers Refactored Application Service Methods: 1 Unify interface to all application services 2 Can be wrapped (e.g. Transaction, Authorization, Logging) 3 Can be enveloped (e.g. REST) Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Command Handlers Rule of thumb: One Command Handler per use Case Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
This is CQRS Client Commands Queries Command Handlers Domain Model O/R Mapper Thin Read Layer Data Store Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
BREAK Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
AGENDA DDD Recap CQRS Step by Step the strategic patterns probably simpler than you think! towards CQRS 1 2 3 4 5 6 „Best Practice“ Domain Events End what we call an Architecture are first class citizens Questions & Answers Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Domain Event Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Domain Event captures the memory of something interesting affecting the domain Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Domain Event the essence is to capture events that trigger a change to the state Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Domain Event event objects are processed to cause the respective change Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Domain Event and stored to provide an audit log Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Shopping Cart Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
we don‘t know: What led to this state? Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Added to Cart Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Added Added to to Cart Cart Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Added Added Added to to to Cart Cart Cart Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Added Added Added Removed to to to from Cart Cart Cart Cart Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Which model contains more information? Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Shopping Cart Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Added Added Added Removed to to to from Cart Cart Cart Cart Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
what if we capture every single event? Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
… and reproduce state from this stream of events? Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
An Event Stream … Added Added Added Removed to to to from Cart Cart Cart Cart Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
An Event Stream … Added Added Added Removed to to to from Cart Cart Cart Cart Shopping Cart Can be projected into: Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
An Event Stream … Added Added Added Removed to to to from Cart Cart Cart Cart Sales History Shopping Cart … or into this: Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
An Event Stream … Added Added Added Removed to to to from Cart Cart Cart Cart Sales History Audit Trail Shopping Cart … or into this: Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
An Event Stream … Added Added Added Removed to to to from Cart Cart Cart Cart Sales History Audit Trail Shopping Campaign Effectiveness Cart … or into this: Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
AGENDA DDD Recap CQRS Step by Step the strategic patterns probably simpler than you think! towards CQRS 1 2 3 4 5 6 „Best Practice“ Domain Events End what we call an Architecture are first class citizens Questions & Answers Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Client Commands Queries Command Handlers Domain Model O/R Mapper Thin Read Layer Data Store Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Client Commands Queries Command Handlers Domain Model O/R Mapper Thin Read Layer SQL Data Store Views Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Client Commands Queries Command Handlers Domain Model O/R Mapper Thin Read Layer INNER JOIN … SQL LEFT OUTER JOIN … Data Store Views UNION … GROUP BY … Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Client Commands Queries Command Handlers Domain Model O/R Mapper Thin Read Layer SELECT * FROM … Table Data Store per Query Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Client Commands Queries Command Handlers Domain Model O/R Mapper Thin Read Layer Table Data Store per Query Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Client Commands Queries Command Handlers Domain Model O/R Mapper Thin Read Layer Event Table Data Store per Query Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Client Commands Queries Command Handlers Domain Model O/R Mapper Thin Read Layer Event Event Table Data Store per Query Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Client Commands Queries Command Handlers Domain Model O/R Mapper Thin Read Layer Event Event Event Table Data Store per Query Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Simplified: Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Events Domain Read Model Commands DTOs Client Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Some Code Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
if ISBN exists in ShoppingCartDetails Increase Amount else Add New Row Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
if Shopping Cart ID exists in ShoppingCartSummary Increase NumberOfItems Add OfferedPrice to TotalAmount else Add New Row Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
if Amount > 1 ShoppingCartDetails Decrease Amount else Delete Row Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Subtract OfferedPrice to TotalAmount Decrease NumberOfItems Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Testability Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Testing the Write Model Command Handlers Domain Model Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Testing the Write Model Command Handlers Given that certain Events happened Domain Model Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Testing the Write Model When a specific Command is sent Command Handlers Given that certain Events happened Domain Model Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Testing the Write Model When a specific Command is sent Command Handlers Given that certain Events happened Domain Model Event Event Then certain Events (and only those!) should be emitted Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Testing the Read Model Thin Read Layer Table per Query Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Testing the Read Model Thin Read Layer Given that certain Events happened Table per Query Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Testing the Read Model Thin Read Layer Given that certain Events happened Table per When a specific Event happens Query Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Testing the Read Model Then each query should return the expected results Thin Read Layer Given that certain Events happened Table per When a specific Event happens Query Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Main Values Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Main Values additive only we don‘t lose information Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Main Values linearly scalable and distributable Read Model Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Main Values every new view can be created from the beginning of time Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Main Values We can come up with new questions at any time Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Main Values built-in integration model Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Proven Technology Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
mature business models move away from Update/Delete and become purely transactional Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
Human resources Medicine Bookkeeping Banking Finances Government … Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
AGENDA DDD Recap CQRS Step by Step the strategic patterns probably simpler than you think! towards CQRS 1 2 3 4 5 6 „Best Practice“ Domain Events End what we call an Architecture are first class citizens Questions & Answers Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
? QUESTIONS Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
THANK YOU! follow me: @dtraub Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de

Recommended

An Introduction to CQRS
An Introduction to CQRSAn Introduction to CQRS
An Introduction to CQRSDennis Traub
 
Strategic Appplication Development with Domain-Driven Design (DDD)
Strategic Appplication Development with Domain-Driven Design (DDD)Strategic Appplication Development with Domain-Driven Design (DDD)
Strategic Appplication Development with Domain-Driven Design (DDD)Dennis Traub
 
Strategischer Anwendungsentwurf mit Domain-Driven Design
Strategischer Anwendungsentwurf mit Domain-Driven DesignStrategischer Anwendungsentwurf mit Domain-Driven Design
Strategischer Anwendungsentwurf mit Domain-Driven DesignDennis Traub
 
Entergence
EntergenceEntergence
Entergencetripiyush
 
Cdp Colour Print Fact Sheet A W
Cdp Colour Print Fact Sheet A WCdp Colour Print Fact Sheet A W
Cdp Colour Print Fact Sheet A WCDP Print Management
 
Taming the Monolith - Microservices Meetup Hamburg
Taming the Monolith - Microservices Meetup HamburgTaming the Monolith - Microservices Meetup Hamburg
Taming the Monolith - Microservices Meetup HamburgDennis Traub
 
CQRS-Einführung - Teil 2
CQRS-Einführung - Teil 2CQRS-Einführung - Teil 2
CQRS-Einführung - Teil 2Dennis Traub
 
CQRS - Eine Einführung - NOUG 2011
CQRS - Eine Einführung - NOUG 2011CQRS - Eine Einführung - NOUG 2011
CQRS - Eine Einführung - NOUG 2011Dennis Traub
 

Recommended

An Introduction to CQRS
An Introduction to CQRSAn Introduction to CQRS
An Introduction to CQRSDennis Traub
 
Strategic Appplication Development with Domain-Driven Design (DDD)
Strategic Appplication Development with Domain-Driven Design (DDD)Strategic Appplication Development with Domain-Driven Design (DDD)
Strategic Appplication Development with Domain-Driven Design (DDD)Dennis Traub
 
Strategischer Anwendungsentwurf mit Domain-Driven Design
Strategischer Anwendungsentwurf mit Domain-Driven DesignStrategischer Anwendungsentwurf mit Domain-Driven Design
Strategischer Anwendungsentwurf mit Domain-Driven DesignDennis Traub
 
Entergence
EntergenceEntergence
Entergencetripiyush
 
Cdp Colour Print Fact Sheet A W
Cdp Colour Print Fact Sheet A WCdp Colour Print Fact Sheet A W
Cdp Colour Print Fact Sheet A WCDP Print Management
 
Taming the Monolith - Microservices Meetup Hamburg
Taming the Monolith - Microservices Meetup HamburgTaming the Monolith - Microservices Meetup Hamburg
Taming the Monolith - Microservices Meetup HamburgDennis Traub
 
CQRS-Einführung - Teil 2
CQRS-Einführung - Teil 2CQRS-Einführung - Teil 2
CQRS-Einführung - Teil 2Dennis Traub
 
CQRS - Eine Einführung - NOUG 2011
CQRS - Eine Einführung - NOUG 2011CQRS - Eine Einführung - NOUG 2011
CQRS - Eine Einführung - NOUG 2011Dennis Traub
 
Sunny Tech 2019 - Craft Forever
Sunny Tech 2019 - Craft ForeverSunny Tech 2019 - Craft Forever
Sunny Tech 2019 - Craft ForeverCyrille Martraire
 
Finding balance of DDD while your application grows
Finding balance of DDD while your application growsFinding balance of DDD while your application grows
Finding balance of DDD while your application growsCarolina Karklis
 
Let's go to the whiteboard: how and why software developers use drawings
Let's go to the whiteboard: how and why software developers use drawingsLet's go to the whiteboard: how and why software developers use drawings
Let's go to the whiteboard: how and why software developers use drawingsMauro Cherubini
 
ITCamp 2012 - Sergiu Damian - Architectural decisions on the battlefield
ITCamp 2012 - Sergiu Damian - Architectural decisions on the battlefieldITCamp 2012 - Sergiu Damian - Architectural decisions on the battlefield
ITCamp 2012 - Sergiu Damian - Architectural decisions on the battlefieldITCamp
 
DOMAIN DRIVER DESIGN
DOMAIN DRIVER DESIGNDOMAIN DRIVER DESIGN
DOMAIN DRIVER DESIGNMohammed Fazuluddin
 
DDD knowledge sharing
DDD knowledge sharingDDD knowledge sharing
DDD knowledge sharingMd. Sadhan Sarker
 
Domain driven design - Part I
Domain driven design - Part IDomain driven design - Part I
Domain driven design - Part INarendran Solai Sridharan
 
Agile Architecture (Scrum + DevOps) by Milan Chheda
Agile Architecture (Scrum + DevOps) by Milan ChhedaAgile Architecture (Scrum + DevOps) by Milan Chheda
Agile Architecture (Scrum + DevOps) by Milan ChhedaAgile ME
 
DDD In Agile
DDD In Agile DDD In Agile
DDD In Agile Skills Matter
 
DaraBaf
DaraBafDaraBaf
DaraBafdarabaf
 
Swarup 7.0 cv
Swarup 7.0 cvSwarup 7.0 cv
Swarup 7.0 cvSwarup Das
 
designertoday0809
designertoday0809designertoday0809
designertoday0809tutorialsruby
 
designertoday0809
designertoday0809designertoday0809
designertoday0809tutorialsruby
 
Soliworks presentation
Soliworks presentationSoliworks presentation
Soliworks presentationSimranjit Singh
 
BDD presentation
BDD presentationBDD presentation
BDD presentationtemebele
 
Rethink your architecture - Marten Deinum
Rethink your architecture - Marten DeinumRethink your architecture - Marten Deinum
Rethink your architecture - Marten DeinumNLJUG
 
Factors of cost for 3d exterior rendering
Factors of cost for 3d exterior rendering Factors of cost for 3d exterior rendering
Factors of cost for 3d exterior rendering Architectural Visualization Studio
 
DNetZone Corporate profile
DNetZone Corporate profileDNetZone Corporate profile
DNetZone Corporate profileDhawal Damania
 
Product Development Brochure
Product Development BrochureProduct Development Brochure
Product Development BrochureMintzlaff Design, Inc.
 
Dashlane Triple Track
Dashlane Triple TrackDashlane Triple Track
Dashlane Triple TrackDashlane
 
Application Integration Patterns (not only) for Microservices
Application Integration Patterns (not only) for MicroservicesApplication Integration Patterns (not only) for Microservices
Application Integration Patterns (not only) for MicroservicesDennis Traub
 
Serverless SecOps Automation on AWS at AWS UG Krakow, Poland
Serverless SecOps Automation on AWS at AWS UG Krakow, PolandServerless SecOps Automation on AWS at AWS UG Krakow, Poland
Serverless SecOps Automation on AWS at AWS UG Krakow, PolandDennis Traub
 

More Related Content

Similar to From DDD to CQRS

Sunny Tech 2019 - Craft Forever
Sunny Tech 2019 - Craft ForeverSunny Tech 2019 - Craft Forever
Sunny Tech 2019 - Craft ForeverCyrille Martraire
 
Finding balance of DDD while your application grows
Finding balance of DDD while your application growsFinding balance of DDD while your application grows
Finding balance of DDD while your application growsCarolina Karklis
 
Let's go to the whiteboard: how and why software developers use drawings
Let's go to the whiteboard: how and why software developers use drawingsLet's go to the whiteboard: how and why software developers use drawings
Let's go to the whiteboard: how and why software developers use drawingsMauro Cherubini
 
ITCamp 2012 - Sergiu Damian - Architectural decisions on the battlefield
ITCamp 2012 - Sergiu Damian - Architectural decisions on the battlefieldITCamp 2012 - Sergiu Damian - Architectural decisions on the battlefield
ITCamp 2012 - Sergiu Damian - Architectural decisions on the battlefieldITCamp
 
Agile Architecture (Scrum + DevOps) by Milan Chheda
Agile Architecture (Scrum + DevOps) by Milan ChhedaAgile Architecture (Scrum + DevOps) by Milan Chheda
Agile Architecture (Scrum + DevOps) by Milan ChhedaAgile ME
 
BDD presentation
BDD presentationBDD presentation
BDD presentationtemebele
 
Rethink your architecture - Marten Deinum
Rethink your architecture - Marten DeinumRethink your architecture - Marten Deinum
Rethink your architecture - Marten DeinumNLJUG
 
DNetZone Corporate profile
DNetZone Corporate profileDNetZone Corporate profile
DNetZone Corporate profileDhawal Damania
 
Dashlane Triple Track
Dashlane Triple TrackDashlane Triple Track
Dashlane Triple TrackDashlane
 

Similar to From DDD to CQRS (20)

Sunny Tech 2019 - Craft Forever
Sunny Tech 2019 - Craft ForeverSunny Tech 2019 - Craft Forever
Sunny Tech 2019 - Craft Forever
 
Finding balance of DDD while your application grows
Finding balance of DDD while your application growsFinding balance of DDD while your application grows
Finding balance of DDD while your application grows
 
Let's go to the whiteboard: how and why software developers use drawings
Let's go to the whiteboard: how and why software developers use drawingsLet's go to the whiteboard: how and why software developers use drawings
Let's go to the whiteboard: how and why software developers use drawings
 
ITCamp 2012 - Sergiu Damian - Architectural decisions on the battlefield
ITCamp 2012 - Sergiu Damian - Architectural decisions on the battlefieldITCamp 2012 - Sergiu Damian - Architectural decisions on the battlefield
ITCamp 2012 - Sergiu Damian - Architectural decisions on the battlefield
 
DOMAIN DRIVER DESIGN
DOMAIN DRIVER DESIGNDOMAIN DRIVER DESIGN
DOMAIN DRIVER DESIGN
 
DDD knowledge sharing
DDD knowledge sharingDDD knowledge sharing
DDD knowledge sharing
 
Domain driven design - Part I
Domain driven design - Part IDomain driven design - Part I
Domain driven design - Part I
 
Agile Architecture (Scrum + DevOps) by Milan Chheda
Agile Architecture (Scrum + DevOps) by Milan ChhedaAgile Architecture (Scrum + DevOps) by Milan Chheda
Agile Architecture (Scrum + DevOps) by Milan Chheda
 
DDD In Agile
DDD In Agile DDD In Agile
DDD In Agile
 
DaraBaf
DaraBafDaraBaf
DaraBaf
 
Swarup 7.0 cv
Swarup 7.0 cvSwarup 7.0 cv
Swarup 7.0 cv
 
designertoday0809
designertoday0809designertoday0809
designertoday0809
 
designertoday0809
designertoday0809designertoday0809
designertoday0809
 
Soliworks presentation
Soliworks presentationSoliworks presentation
Soliworks presentation
 
BDD presentation
BDD presentationBDD presentation
BDD presentation
 
Rethink your architecture - Marten Deinum
Rethink your architecture - Marten DeinumRethink your architecture - Marten Deinum
Rethink your architecture - Marten Deinum
 
Factors of cost for 3d exterior rendering
Factors of cost for 3d exterior rendering Factors of cost for 3d exterior rendering
Factors of cost for 3d exterior rendering
 
DNetZone Corporate profile
DNetZone Corporate profileDNetZone Corporate profile
DNetZone Corporate profile
 
Product Development Brochure
Product Development BrochureProduct Development Brochure
Product Development Brochure
 
Dashlane Triple Track
Dashlane Triple TrackDashlane Triple Track
Dashlane Triple Track
 

More from Dennis Traub

Application Integration Patterns (not only) for Microservices
Application Integration Patterns (not only) for MicroservicesApplication Integration Patterns (not only) for Microservices
Application Integration Patterns (not only) for MicroservicesDennis Traub
 
Serverless SecOps Automation on AWS at AWS UG Krakow, Poland
Serverless SecOps Automation on AWS at AWS UG Krakow, PolandServerless SecOps Automation on AWS at AWS UG Krakow, Poland
Serverless SecOps Automation on AWS at AWS UG Krakow, PolandDennis Traub
 
Serverless Security Automation on AWS - Hamburg AWS User Group
Serverless Security Automation on AWS - Hamburg AWS User GroupServerless Security Automation on AWS - Hamburg AWS User Group
Serverless Security Automation on AWS - Hamburg AWS User GroupDennis Traub
 
Cloud ist keine Strategie - Keynote des AWS Cloud Day, Solingen
Cloud ist keine Strategie - Keynote des AWS Cloud Day, SolingenCloud ist keine Strategie - Keynote des AWS Cloud Day, Solingen
Cloud ist keine Strategie - Keynote des AWS Cloud Day, SolingenDennis Traub
 
Cloud ist keine Strategie - AWS Tech Community Summit Cologne, 2017
Cloud ist keine Strategie - AWS Tech Community Summit Cologne, 2017Cloud ist keine Strategie - AWS Tech Community Summit Cologne, 2017
Cloud ist keine Strategie - AWS Tech Community Summit Cologne, 2017Dennis Traub
 
Taming the Monolith
Taming the MonolithTaming the Monolith
Taming the MonolithDennis Traub
 
DDD / Microservices @ Trivento Spring Camp, Utrecht, 2015
DDD / Microservices @ Trivento Spring Camp, Utrecht, 2015DDD / Microservices @ Trivento Spring Camp, Utrecht, 2015
DDD / Microservices @ Trivento Spring Camp, Utrecht, 2015Dennis Traub
 
DDD Modeling Workshop
DDD Modeling WorkshopDDD Modeling Workshop
DDD Modeling WorkshopDennis Traub
 

More from Dennis Traub (8)

Application Integration Patterns (not only) for Microservices
Application Integration Patterns (not only) for MicroservicesApplication Integration Patterns (not only) for Microservices
Application Integration Patterns (not only) for Microservices
 
Serverless SecOps Automation on AWS at AWS UG Krakow, Poland
Serverless SecOps Automation on AWS at AWS UG Krakow, PolandServerless SecOps Automation on AWS at AWS UG Krakow, Poland
Serverless SecOps Automation on AWS at AWS UG Krakow, Poland
 
Serverless Security Automation on AWS - Hamburg AWS User Group
Serverless Security Automation on AWS - Hamburg AWS User GroupServerless Security Automation on AWS - Hamburg AWS User Group
Serverless Security Automation on AWS - Hamburg AWS User Group
 
Cloud ist keine Strategie - Keynote des AWS Cloud Day, Solingen
Cloud ist keine Strategie - Keynote des AWS Cloud Day, SolingenCloud ist keine Strategie - Keynote des AWS Cloud Day, Solingen
Cloud ist keine Strategie - Keynote des AWS Cloud Day, Solingen
 
Cloud ist keine Strategie - AWS Tech Community Summit Cologne, 2017
Cloud ist keine Strategie - AWS Tech Community Summit Cologne, 2017Cloud ist keine Strategie - AWS Tech Community Summit Cologne, 2017
Cloud ist keine Strategie - AWS Tech Community Summit Cologne, 2017
 
Taming the Monolith
Taming the MonolithTaming the Monolith
Taming the Monolith
 
DDD / Microservices @ Trivento Spring Camp, Utrecht, 2015
DDD / Microservices @ Trivento Spring Camp, Utrecht, 2015DDD / Microservices @ Trivento Spring Camp, Utrecht, 2015
DDD / Microservices @ Trivento Spring Camp, Utrecht, 2015
 
DDD Modeling Workshop
DDD Modeling WorkshopDDD Modeling Workshop
DDD Modeling Workshop
 

Recently uploaded

AWS Community Day CPH - Three problems of Terraform
AWS Community Day CPH - Three problems of TerraformAWS Community Day CPH - Three problems of Terraform
AWS Community Day CPH - Three problems of TerraformAndrey Devyatkin
 
Elevate Developer Efficiency & build GenAI Application with Amazon Q​
Elevate Developer Efficiency & build GenAI Application with Amazon Q​Elevate Developer Efficiency & build GenAI Application with Amazon Q​
Elevate Developer Efficiency & build GenAI Application with Amazon Q​Bhuvaneswari Subramani
 
"I see eyes in my soup": How Delivery Hero implemented the safety system for ...
"I see eyes in my soup": How Delivery Hero implemented the safety system for ..."I see eyes in my soup": How Delivery Hero implemented the safety system for ...
"I see eyes in my soup": How Delivery Hero implemented the safety system for ...Zilliz
 
Introduction to Multilingual Retrieval Augmented Generation (RAG)
Introduction to Multilingual Retrieval Augmented Generation (RAG)Introduction to Multilingual Retrieval Augmented Generation (RAG)
Introduction to Multilingual Retrieval Augmented Generation (RAG)Zilliz
 
Modular Monolith - a Practical Alternative to Microservices @ Devoxx UK 2024
Modular Monolith - a Practical Alternative to Microservices @ Devoxx UK 2024Modular Monolith - a Practical Alternative to Microservices @ Devoxx UK 2024
Modular Monolith - a Practical Alternative to Microservices @ Devoxx UK 2024Victor Rentea
 
Apidays New York 2024 - Accelerating FinTech Innovation by Vasa Krishnan, Fin...
Apidays New York 2024 - Accelerating FinTech Innovation by Vasa Krishnan, Fin...Apidays New York 2024 - Accelerating FinTech Innovation by Vasa Krishnan, Fin...
Apidays New York 2024 - Accelerating FinTech Innovation by Vasa Krishnan, Fin...apidays
 
Artificial Intelligence Chap.5 : Uncertainty
Artificial Intelligence Chap.5 : UncertaintyArtificial Intelligence Chap.5 : Uncertainty
Artificial Intelligence Chap.5 : UncertaintyKhushali Kathiriya
 
Polkadot JAM Slides - Token2049 - By Dr. Gavin Wood
Polkadot JAM Slides - Token2049 - By Dr. Gavin WoodPolkadot JAM Slides - Token2049 - By Dr. Gavin Wood
Polkadot JAM Slides - Token2049 - By Dr. Gavin WoodJuan lago vázquez
 
Apidays New York 2024 - The Good, the Bad and the Governed by David O'Neill, ...
Apidays New York 2024 - The Good, the Bad and the Governed by David O'Neill, ...Apidays New York 2024 - The Good, the Bad and the Governed by David O'Neill, ...
Apidays New York 2024 - The Good, the Bad and the Governed by David O'Neill, ...apidays
 
TrustArc Webinar - Unlock the Power of AI-Driven Data Discovery
TrustArc Webinar - Unlock the Power of AI-Driven Data DiscoveryTrustArc Webinar - Unlock the Power of AI-Driven Data Discovery
TrustArc Webinar - Unlock the Power of AI-Driven Data DiscoveryTrustArc
 
FWD Group - Insurer Innovation Award 2024
FWD Group - Insurer Innovation Award 2024FWD Group - Insurer Innovation Award 2024
FWD Group - Insurer Innovation Award 2024The Digital Insurer
 
Mcleodganj Call Girls 🥰 8617370543 Service Offer VIP Hot Model
Mcleodganj Call Girls 🥰 8617370543 Service Offer VIP Hot ModelMcleodganj Call Girls 🥰 8617370543 Service Offer VIP Hot Model
Mcleodganj Call Girls 🥰 8617370543 Service Offer VIP Hot ModelDeepika Singh
 
Exploring Multimodal Embeddings with Milvus
Exploring Multimodal Embeddings with MilvusExploring Multimodal Embeddings with Milvus
Exploring Multimodal Embeddings with MilvusZilliz
 
Connector Corner: Accelerate revenue generation using UiPath API-centric busi...
Connector Corner: Accelerate revenue generation using UiPath API-centric busi...Connector Corner: Accelerate revenue generation using UiPath API-centric busi...
Connector Corner: Accelerate revenue generation using UiPath API-centric busi...DianaGray10
 
ICT role in 21st century education and its challenges
ICT role in 21st century education and its challengesICT role in 21st century education and its challenges
ICT role in 21st century education and its challengesrafiqahmad00786416
 
MINDCTI Revenue Release Quarter One 2024
MINDCTI Revenue Release Quarter One 2024MINDCTI Revenue Release Quarter One 2024
MINDCTI Revenue Release Quarter One 2024MIND CTI
 
Strategies for Landing an Oracle DBA Job as a Fresher
Strategies for Landing an Oracle DBA Job as a FresherStrategies for Landing an Oracle DBA Job as a Fresher
Strategies for Landing an Oracle DBA Job as a FresherRemote DBA Services
 
Navigating the Deluge_ Dubai Floods and the Resilience of Dubai International...
Navigating the Deluge_ Dubai Floods and the Resilience of Dubai International...Navigating the Deluge_ Dubai Floods and the Resilience of Dubai International...
Navigating the Deluge_ Dubai Floods and the Resilience of Dubai International...Orbitshub
 
Corporate and higher education May webinar.pptx
Corporate and higher education May webinar.pptxCorporate and higher education May webinar.pptx
Corporate and higher education May webinar.pptxRustici Software
 

Recently uploaded (20)

AWS Community Day CPH - Three problems of Terraform
AWS Community Day CPH - Three problems of TerraformAWS Community Day CPH - Three problems of Terraform
AWS Community Day CPH - Three problems of Terraform
 
Elevate Developer Efficiency & build GenAI Application with Amazon Q​
Elevate Developer Efficiency & build GenAI Application with Amazon Q​Elevate Developer Efficiency & build GenAI Application with Amazon Q​
Elevate Developer Efficiency & build GenAI Application with Amazon Q​
 
"I see eyes in my soup": How Delivery Hero implemented the safety system for ...
"I see eyes in my soup": How Delivery Hero implemented the safety system for ..."I see eyes in my soup": How Delivery Hero implemented the safety system for ...
"I see eyes in my soup": How Delivery Hero implemented the safety system for ...
 
Introduction to Multilingual Retrieval Augmented Generation (RAG)
Introduction to Multilingual Retrieval Augmented Generation (RAG)Introduction to Multilingual Retrieval Augmented Generation (RAG)
Introduction to Multilingual Retrieval Augmented Generation (RAG)
 
Modular Monolith - a Practical Alternative to Microservices @ Devoxx UK 2024
Modular Monolith - a Practical Alternative to Microservices @ Devoxx UK 2024Modular Monolith - a Practical Alternative to Microservices @ Devoxx UK 2024
Modular Monolith - a Practical Alternative to Microservices @ Devoxx UK 2024
 
Apidays New York 2024 - Accelerating FinTech Innovation by Vasa Krishnan, Fin...
Apidays New York 2024 - Accelerating FinTech Innovation by Vasa Krishnan, Fin...Apidays New York 2024 - Accelerating FinTech Innovation by Vasa Krishnan, Fin...
Apidays New York 2024 - Accelerating FinTech Innovation by Vasa Krishnan, Fin...
 
Artificial Intelligence Chap.5 : Uncertainty
Artificial Intelligence Chap.5 : UncertaintyArtificial Intelligence Chap.5 : Uncertainty
Artificial Intelligence Chap.5 : Uncertainty
 
Polkadot JAM Slides - Token2049 - By Dr. Gavin Wood
Polkadot JAM Slides - Token2049 - By Dr. Gavin WoodPolkadot JAM Slides - Token2049 - By Dr. Gavin Wood
Polkadot JAM Slides - Token2049 - By Dr. Gavin Wood
 
Apidays New York 2024 - The Good, the Bad and the Governed by David O'Neill, ...
Apidays New York 2024 - The Good, the Bad and the Governed by David O'Neill, ...Apidays New York 2024 - The Good, the Bad and the Governed by David O'Neill, ...
Apidays New York 2024 - The Good, the Bad and the Governed by David O'Neill, ...
 
TrustArc Webinar - Unlock the Power of AI-Driven Data Discovery
TrustArc Webinar - Unlock the Power of AI-Driven Data DiscoveryTrustArc Webinar - Unlock the Power of AI-Driven Data Discovery
TrustArc Webinar - Unlock the Power of AI-Driven Data Discovery
 
FWD Group - Insurer Innovation Award 2024
FWD Group - Insurer Innovation Award 2024FWD Group - Insurer Innovation Award 2024
FWD Group - Insurer Innovation Award 2024
 
Mcleodganj Call Girls 🥰 8617370543 Service Offer VIP Hot Model
Mcleodganj Call Girls 🥰 8617370543 Service Offer VIP Hot ModelMcleodganj Call Girls 🥰 8617370543 Service Offer VIP Hot Model
Mcleodganj Call Girls 🥰 8617370543 Service Offer VIP Hot Model
 
Exploring Multimodal Embeddings with Milvus
Exploring Multimodal Embeddings with MilvusExploring Multimodal Embeddings with Milvus
Exploring Multimodal Embeddings with Milvus
 
Connector Corner: Accelerate revenue generation using UiPath API-centric busi...
Connector Corner: Accelerate revenue generation using UiPath API-centric busi...Connector Corner: Accelerate revenue generation using UiPath API-centric busi...
Connector Corner: Accelerate revenue generation using UiPath API-centric busi...
 
ICT role in 21st century education and its challenges
ICT role in 21st century education and its challengesICT role in 21st century education and its challenges
ICT role in 21st century education and its challenges
 
MINDCTI Revenue Release Quarter One 2024
MINDCTI Revenue Release Quarter One 2024MINDCTI Revenue Release Quarter One 2024
MINDCTI Revenue Release Quarter One 2024
 
+971581248768>> SAFE AND ORIGINAL ABORTION PILLS FOR SALE IN DUBAI AND ABUDHA...
+971581248768>> SAFE AND ORIGINAL ABORTION PILLS FOR SALE IN DUBAI AND ABUDHA...+971581248768>> SAFE AND ORIGINAL ABORTION PILLS FOR SALE IN DUBAI AND ABUDHA...
+971581248768>> SAFE AND ORIGINAL ABORTION PILLS FOR SALE IN DUBAI AND ABUDHA...
 
Strategies for Landing an Oracle DBA Job as a Fresher
Strategies for Landing an Oracle DBA Job as a FresherStrategies for Landing an Oracle DBA Job as a Fresher
Strategies for Landing an Oracle DBA Job as a Fresher
 
Navigating the Deluge_ Dubai Floods and the Resilience of Dubai International...
Navigating the Deluge_ Dubai Floods and the Resilience of Dubai International...Navigating the Deluge_ Dubai Floods and the Resilience of Dubai International...
Navigating the Deluge_ Dubai Floods and the Resilience of Dubai International...
 
Corporate and higher education May webinar.pptx
Corporate and higher education May webinar.pptxCorporate and higher education May webinar.pptx
Corporate and higher education May webinar.pptx
 

From DDD to CQRS

  • 1. From DDD to CQRS presented by Dennis Traub .NET Usergroup Bern - 19. März 2013 Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 2. Who‘s that guy? Dennis Traub Founder, Owner, CEO, Single Employee of D. Traub Software Development Consultancy Consultant, developer, trainer, speaker 39 years old Married, father of one 20+ years in software development Hire me at mail@dennistraub.de @dtraub Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 3. AGENDA DDD Recap CQRS Break Step by Step the strategic patterns probably simpler than you think! towards CQRS 1 2 3 4 5 6 „Best Practice“ Domain Events End what we call an Architecture are first class citizens Questions & Answers Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 4. AGENDA DDD Recap CQRS Step by Step the strategic patterns probably simpler than you think! towards CQRS 1 2 3 4 5 6 „Best Practice“ Domain Events End what we call an Architecture are first class citizens Questions & Answers Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 5. The „Blue Book“ by Eric Evans Image Placeholder Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 6. Domain-Driven Design Domain Service Value Object Aggregate Specification The well- known Reposit ory Patterns Entity Factory And so on . . Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 7. Domain-Driven Design Ubiquit ous Language Core Domain Domain Expert Bounded Context The important Domain Model Patterns (Generic) Subdomains Context Map And so on . . Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 8. don‘t build one big model that works for everyone Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 9. the tactical Building Blocks we don‘t use DDD when there is no value in formalizing the problem Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 10. we only use DDD in parts where we get a competitive advantage Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 11. we focus our effort and resources on the most important subdomain Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 12. a.k.a. The Core Domain Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 13. AGENDA DDD Recap CQRS Step by Step the strategic patterns probably simpler than you think! towards CQRS 1 2 3 4 5 6 „Best Practice“ Domain Events End what we call an Architecture are first class citizens Questions & Answers Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 14. Presentation Layer Application Services Domain / Business Model / BLL DAL / O/R-Mapper Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 15. Pros of the „Best Practice Architecture“ 1 Easy to build 2 Accepted by management 3 Well-know throughall all seniority levels 4 We know ist limitiations Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 16. Cons of the „Best Practice Architecture“ 1 Limited scalability 2 Loss of intent 3 Lazy loading, locking, race conditions, … 4 Few classes do way too much stuff Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 17. And: If the model is basically CRUD where does Business Logic live? Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 18. Domain Model Responsibilities 1 Business Logic 6 Aggregation 2 Validation 7 Presentation 3 Structure 8 Persistence 4 Projection 9 Processes 5 Associations 10 Lazy / Eager Loading Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 19. the S in SOLID Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 20. Single Responsibility Principle just because we can doesn‘t mean we should Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 21. why do we try to build One Model to Rule Them All? Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 22. reading and writing are completely different from eachother Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 23. Sometimes it‘s cheaper to do two things than dealing with the trade-offs Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 24. AGENDA DDD Recap CQRS Step by Step the strategic patterns probably simpler than you think! towards CQRS 1 2 3 4 5 6 „Best Practice“ Domain Events End what we call an Architecture are first class citizens Questions & Answers Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 25. Command Query Separation Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 26. Command Query Separation (CQS) „Every method should either be a command that performs an action or a query that returns data to the caller“ -- Dr. Bertrand Meyer Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 27. Command Query Separation (CQS) in other words: Asking a question should not change the answer Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 28. Command/Query Responsability Segregation Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 29. CQS on an Architectural Level Queries Commands Project Details Project List Project Data Store Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 30. Queries and Projection (Read) Show something Thin Read Layer Data Store Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 31. Thin Read Layer Concerns: 1 Filtering, Scope 2 Data Presentation Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 32. Thin Read Layer Attributes: 1 Data-Oriented 2 Indexable 3 Can be denormalized and distributed for fast access 4 Only Structure Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 33. Behavior and Modification (Write) Do something Command Handler Domain Model O/R-Mapper Data Store Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 34. Domain Model Concerns: 1 Business Logic 2 Validation Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 35. Domain Model Attributes: 1 Normalized 2 Transactional 3 Object-Oriented 4 Persistence Ignorant 5 Only Behavior Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 36. Commands Refactor Application Service Calls to Objects 1 Serializable 2 Can be enveloped 3 Can be intercepted 4 Can be enriched 5 Communicate intent Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 37. Command Handlers Refactored Application Service Methods: 1 Unify interface to all application services 2 Can be wrapped (e.g. Transaction, Authorization, Logging) 3 Can be enveloped (e.g. REST) Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 38. Command Handlers Rule of thumb: One Command Handler per use Case Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 39. This is CQRS Client Commands Queries Command Handlers Domain Model O/R Mapper Thin Read Layer Data Store Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 40. BREAK Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 41. AGENDA DDD Recap CQRS Step by Step the strategic patterns probably simpler than you think! towards CQRS 1 2 3 4 5 6 „Best Practice“ Domain Events End what we call an Architecture are first class citizens Questions & Answers Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 42. Domain Event Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 43. Domain Event captures the memory of something interesting affecting the domain Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 44. Domain Event the essence is to capture events that trigger a change to the state Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 45. Domain Event event objects are processed to cause the respective change Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 46. Domain Event and stored to provide an audit log Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 47. Shopping Cart Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 48. we don‘t know: What led to this state? Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 49. Added to Cart Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 50. Added Added to to Cart Cart Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 51. Added Added Added to to to Cart Cart Cart Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 52. Added Added Added Removed to to to from Cart Cart Cart Cart Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 53. Which model contains more information? Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 54. Shopping Cart Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 55. Added Added Added Removed to to to from Cart Cart Cart Cart Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 56. what if we capture every single event? Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 57. … and reproduce state from this stream of events? Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 58. An Event Stream … Added Added Added Removed to to to from Cart Cart Cart Cart Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 59. An Event Stream … Added Added Added Removed to to to from Cart Cart Cart Cart Shopping Cart Can be projected into: Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 60. An Event Stream … Added Added Added Removed to to to from Cart Cart Cart Cart Sales History Shopping Cart … or into this: Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 61. An Event Stream … Added Added Added Removed to to to from Cart Cart Cart Cart Sales History Audit Trail Shopping Cart … or into this: Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 62. An Event Stream … Added Added Added Removed to to to from Cart Cart Cart Cart Sales History Audit Trail Shopping Campaign Effectiveness Cart … or into this: Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 63. AGENDA DDD Recap CQRS Step by Step the strategic patterns probably simpler than you think! towards CQRS 1 2 3 4 5 6 „Best Practice“ Domain Events End what we call an Architecture are first class citizens Questions & Answers Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 64. Client Commands Queries Command Handlers Domain Model O/R Mapper Thin Read Layer Data Store Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 65. Client Commands Queries Command Handlers Domain Model O/R Mapper Thin Read Layer SQL Data Store Views Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 66. Client Commands Queries Command Handlers Domain Model O/R Mapper Thin Read Layer INNER JOIN … SQL LEFT OUTER JOIN … Data Store Views UNION … GROUP BY … Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 67. Client Commands Queries Command Handlers Domain Model O/R Mapper Thin Read Layer SELECT * FROM … Table Data Store per Query Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 68. Client Commands Queries Command Handlers Domain Model O/R Mapper Thin Read Layer Table Data Store per Query Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 69. Client Commands Queries Command Handlers Domain Model O/R Mapper Thin Read Layer Event Table Data Store per Query Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 70. Client Commands Queries Command Handlers Domain Model O/R Mapper Thin Read Layer Event Event Table Data Store per Query Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 71. Client Commands Queries Command Handlers Domain Model O/R Mapper Thin Read Layer Event Event Event Table Data Store per Query Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 72. Simplified: Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 73. Events Domain Read Model Commands DTOs Client Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 74. Some Code Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 75. Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 76. Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 77. if ISBN exists in ShoppingCartDetails Increase Amount else Add New Row Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 78. if Shopping Cart ID exists in ShoppingCartSummary Increase NumberOfItems Add OfferedPrice to TotalAmount else Add New Row Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 79. Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 80. Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 81. if Amount > 1 ShoppingCartDetails Decrease Amount else Delete Row Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 82. Subtract OfferedPrice to TotalAmount Decrease NumberOfItems Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 83. Testability Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 84. Testing the Write Model Command Handlers Domain Model Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 85. Testing the Write Model Command Handlers Given that certain Events happened Domain Model Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 86. Testing the Write Model When a specific Command is sent Command Handlers Given that certain Events happened Domain Model Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 87. Testing the Write Model When a specific Command is sent Command Handlers Given that certain Events happened Domain Model Event Event Then certain Events (and only those!) should be emitted Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 88. Testing the Read Model Thin Read Layer Table per Query Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 89. Testing the Read Model Thin Read Layer Given that certain Events happened Table per Query Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 90. Testing the Read Model Thin Read Layer Given that certain Events happened Table per When a specific Event happens Query Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 91. Testing the Read Model Then each query should return the expected results Thin Read Layer Given that certain Events happened Table per When a specific Event happens Query Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 92. Main Values Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 93. Main Values additive only we don‘t lose information Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 94. Main Values linearly scalable and distributable Read Model Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 95. Main Values every new view can be created from the beginning of time Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 96. Main Values We can come up with new questions at any time Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 97. Main Values built-in integration model Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 98. Proven Technology Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 99. mature business models move away from Update/Delete and become purely transactional Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 100. Human resources Medicine Bookkeeping Banking Finances Government … Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 101. AGENDA DDD Recap CQRS Step by Step the strategic patterns probably simpler than you think! towards CQRS 1 2 3 4 5 6 „Best Practice“ Domain Events End what we call an Architecture are first class citizens Questions & Answers Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 102. ? QUESTIONS Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de
  • 103. THANK YOU! follow me: @dtraub Dennis Traub – Software Development Consultancy @dtraub – mail@dennistraub.de