Failures and learnings during the adoption of DDD

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Failures and learnings during the adoption of DDD MICHAEL PLÖD FELLOW

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Michael Plöd Fellow at INNOQ Mastodon (or Twitter): @[email protected] LinkedIn: https://www.linkedin.com/in/michael-ploed/ Current consulting topics: • Domain-Driven Design • Team Topologies • Transformation from IT Delivery to digital product orgs Regular speaker at (inter-)national conferences and author of a book + various articles

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Get my DDD book cheaper Book Voucher: 7.99 instead of (min) 9.99 http://leanpub.com/ddd-by-example/c/speakerdeck

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I have failed a lot with DDD …

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… and learned so much on this path …

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… which was valuable

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Failure #1 Ignorance for culture

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Domain Subdomain Subdomain Bounded Context Tactical Patterns Aggregate, Entity, Value Object, Repository, Service, Factory Bounded Context Tactical Patterns Aggregate, Entity, Value Object, Repository, Service, Factory Bounded Context Tactical Patterns Aggregate, Entity, Value Object, Repository, Service, Factory Strategic DDD Domain Subdomain Bounded Context Context Map Tactical DDD Aggregate Entity Value Object Repository Service Factory

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Those are just two aspects of Domain Driven Design

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ATTITUDE DDD is a culture for domain modeling Strategic DDD Domain Subdomain Bounded Context Context Map Tactical DDD Aggregate Entity Value Object Repository Service Factory

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DDD is a culture for domain modeling Strategic DDD Domain Subdomain Bounded Context Context Map Tactical DDD Aggregate Entity Value Object Repository Service Factory Explicit->implicit Continuous Learning Evolutionary Design Compare Models Language Psychological Safety Collaboration Low entrance barrier

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When the foundation is gone you no langer have a solid base for modeling

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Failure #2 DDDfall

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The promise: Time to market with DDD Photo by Campful on Unsplash

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We aRE AgILe wE aRE dOIng SCrUM Photo by Kelly Sikkema on Unsplash

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Photo by Michael Plöd

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DDD in a waterfall Photo by Ingo Doerrie on Unsplash

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https://github.com/ddd-crew/ddd-starter-modelling-process

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Failure #3 Lack of domain experts

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No access to domain knowledge means No Domain Driven Design

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Domain Expertise can sometimes be hidden in interesting spots that you don’t expect

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Failure #4 Uncollaborative Modelling

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Source: https://amplitude.com/blog/journey-to-product-teams-infographic

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Source: https://amplitude.com/blog/journey-to-product-teams-infographic

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Use collaborative modeling methods with a low entrance barrier Image for example mapping taken from: https://openpracticelibrary.com/practice/example-mapping/ Image for user story mapping taken from: https://www.hanssamios.com/dokuwiki/how_do_we_build_and_maintain_context_when_all_we_have_is_a_backlog_list

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Failure #5 Rebranding

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„Basically we’ve been doing DDD for ages already“

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Object Oriented Analysis and Design was nouns irst

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EventStorming is verbs irst

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Failure #6 Code allergy

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Mind the code probe!!!

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But we need a good design irst

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Photo by Michael Plöd

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Go for code early, prototype, fail, prototype again, fail again, re ine the prototype, re lect your strategic design based on those learnings, learn, go to prod, learn, refactor the code, learn, learn, learn, learn, …

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Failure #7 Pattern stubbornness

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Someone: „You are only doing true DDD if you strictly stick to hexagonal architecture and the tactical patterns everywhere, no exceptions!“

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A gentle comment…

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Mind the purpose … A Bounded Context is a boundary for a model expressed in a consistent language tailored around a speci ic purpose

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If the purpose of a Bounded Context doesn’t call for some of the patterns, don’t use them. Understanding this, acknowledging it and designing your software accordingly is so much more about DDD than blindly sticking to some patterns because they were in a blue book (which is amazing, no diss!).

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Failure #8 Silver Bullet Thinking

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This book is important, a (probably) timeless classic in IT literature. But it’s not a bible and shouldn’t be treated like one.

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Domain Driven Design is not a silver bullet

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- George E. P. Box - All models are wrong, but some are useful

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Failure #9 Terminology ignorance

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Some IT conference Registration of visitors Lunch planning Printing of badges Room planning Selling tickets Handling of payments

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YOU at some IT conference Registration of visitors Lunch planning Printing of badges Room planning Selling tickets Handling of payments

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Don’t Repeat Yourself

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YOU at some IT conference Registration of visitors Lunch planning Printing of badges Room planning Selling tickets Handling of payments

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Bounded Context A Bounded Context is a boundary for a model expressed in a consistent language tailored around a speci ic purpose

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This has no purpose at all and the language is also not speci ic here

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Maybe those are interesting bounded context candidates? Event Management Badges Ticket Sales

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Failure #10 Developer (miss)experience

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https://github.com/ddd-crew/ddd-starter-modelling-process

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https://github.com/ddd-crew/ddd-starter-modelling-process You won’t achieve quick learning cycles with a horrible developer experience

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Failure #11 Hesitance to kill darlings

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A story of a brilliant manager during a 5 day offsite workshop series

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Day 1: EventStorming Photo by Michael Plöd

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Day 2: (Sub)Domains Photo by Michael Plöd

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Day 3: Bounded Contexts Photo by Michael Plöd

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Day 4: Trashing Bounded Contexts Photo by Jilbert Ebrahimi on Unsplash

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Manager: „this looks totally different … where are yesterdays Bounded Contexts“ Team: „we learned something and trashed them for another design“ Day 5: Questions

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Day 5: A toast to the dead contexts !

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Get rid of unsuitable designs

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Failure #12 Fullblown DDD

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Let’s do a DDD project and apply everything.

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An interesting path Photo by Michael Plöd

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To Hekla, one of Icelands most dangerous volcanos Photo by Michael Plöd

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Don’t do full blown DDD just for the sake of it. Just use the concepts that solve your problems. Photo by Michael Plöd

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Get my DDD book cheaper Book Voucher: 7.99 instead of (min) 9.99 http://leanpub.com/ddd-by-example/c/speakerdeck

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Krischerstr. 100 40789 Monheim +49 2173 3366-0 Ohlauer Str. 43 10999 Berlin Ludwigstr. 180E 63067 Offenbach Kreuzstr. 16 80331 München Hermannstrasse 13 20095 Hamburg Erftstr. 15-17 50672 Köln Königstorgraben 11 90402 Nürnberg innoQ Deutschland GmbH www.innoq.com Thank you! Michael Plöd E-Mail: [email protected] Socials: @[email protected] LinkedIn: https://www.linkedin.com/in/michael-ploed/ German version of Team Topologies incl. the Remote Team Interactions Workbook Translated by me Release through O’Reilly Germany in approx. November 2023