Virtual Domain-driven design

We design for high availability assuming connectivity is always present. But what happens when a nationwide power outage leaves warehouses in the dark and cloud systems completely unreachable?

During a major blackout that impacted most of Spain’s power grid, Mercadona Online had thousands of active orders mid-fulfillment across warehouses. While central systems went down, logistics operations had to continue.

In this session, Emilio breaks down the architectural decisions — and the business trade-offs behind them — that made system survival possible:

• Local-first as a first-class citizen: how edge nodes operated in “bunker mode” with on-site compute, keeping warehouse operations running without central systems.
• The split-brain dilemma: managing state divergence between physical reality and the central database, and the rules that determined which side wins.
• The resurrection problem: reconciling millions of offline transactions once connectivity was restored, including race conditions and data recovery challenges.

Every decision in this architecture was driven by real business constraints: SLAs with physical warehouses, perishable goods with expiration times, and logistics costs measured in thousands per minute of downtime.

This is not a theoretical chaos engineering talk — it is a real-world case study of how architectural trade-offs made years earlier kept a critical business running when everything else failed.

In this session, we are joined by Rebecca Wirfs-Brock, who will first present a short talk on their essay Critically Engaging With Models followed by a group discussion. It would be great if you could read their essay beforehand. If you want to support their writing and read more, you can buy their book, Design and Reality: Essays on Software Design

Models, whether for a software system, a development process, diseases, political systems, or otherwise, are a way to look at (a part of) the world. They make a choice about what is important, what categories we classify things in, what we see, what’s invisible, what’s valued, or even what’s valid. They are reductionist, that is, they only show a selection of the subject they’re describing. And they are biased: They implicitly reflect the assumptions, constraints, and values of the model’s author. Most of the time, when you adopt a model created by someone else, you assimilate it into your world view without much thought. You acquire a new way of seeing something. But when you do that, you may not understand the model’s limitations. However, you can choose to look at someone’s model more intentionally. We will share and discuss some tools for critically evaluating any models that come your way. You can assess whether this model fits your needs. If you’re looking at a model for the first time, you can use that fresh perspective to see what the model includes and what it leaves out. Models are a powerful lens for perceiving a subject, and you should be deliberate when wielding them.

Automation is a frequently discussed topic in the development and test communities - and has been for many years. Similarly, patterns have been part of community discourse ever since the Design Patterns book was published in 1994. It appears to us that both suffer from periodic bursts of hype and long stretches of neglect.

While working on the Automation Patterns portion of our new book Effective Behavior-Driven Development, we have had the chance to explore the nuances of context specific automation and pattern forms. Our knowledge of BDD-specific automation styles comes from many years of practical application in industry. However, our experience with patterns has, up until this point, been mainly one of consumption. That changed when we took a subset of our BDD automation patterns to this year’s EuroPLoP pattern workshops — and got a refreshed view of pattern authoring.

We’re happy to share the insights gained and challenges remaining in a conversation with VirtualDDD.

Seb has been a consultant, coach, designer, author and developer for over 40 years. He has been involved in the full development lifecycle with experience that ranges from architecture to support, from C to Visual Basic.

During his career, he has worked for companies large (e.g. IBM, Amazon) and small, and has extensive experience of failed projects. He's now an independent software consultant and author, promoting effective ways of working to the software development and testing community.

Regular speaker at conferences and occasional contributor to software journals. Co-author of "Effective Behaviour Driven Development" (Manning), lead author of “The Cucumber for Java Book” (Pragmatic Programmers), and contributing author to “97 Things Every Programmer Should Know” (O’Reilly).

He blogs at claysnow.co.uk and socialises as [email protected]

Gáspár Nagy, the creator of SpecFlow & Reqnroll, bringing over 20 years of experience as a coach, trainer and test automation expert nowadays through his company, called Spec Solutions. He is the co-author of the books "Discovery: Explore behaviour using examples",  "Formulation: Document examples with Given/When/Then" and "Effective Behavior-Driven Development" and also leads SpecSync, aiding teams in test traceability with Azure DevOps and Jira. He is active in the open-source community through leading the Reqnroll project. Gáspár shares his insights at conferences, emphasizing his commitment to helping teams implement Behavior-Driven Development (BDD).

When developing your software products, be it coding, testing, user experience, product management, or all the other elements required to solve a customer need, do you understand what the rest of the people do to make that happen? What about the other people in your organisation, maybe working on different products or even other legs of the customer journey like sales, customer service, billing, and operations? Do you see how you fit into the big picture, and what your contribution is to the company vision and strategy? I suspect most of us neither have the time nor the opportunity to get a wider view, focusing on our little part of the bigger system instead and making the best of that.

We know that a system is supposed to be more than the sum of its parts, but how can we make sure that the sum is positive? That is hard when we cannot see the forest for the trees.

Let us employ systems thinking to give us a holistic perspective, by adding synthesis to our analysis skills so that we can explore and understand emergence. We all know reductionism well, working on parts in isolation but holism is required to provide important insights and knowledge to handle the complexity in domains we normally work in – especially where people are involved. Only then can we build sustainable and adaptive software systems.

This is an introduction to systems thinking and its importance when dealing with complexity.

About Trond

Senior IT Consultant and sociotechnical practitioner.

Trond is an IT architect and open sociotechnical systems practitioner with extensive experience working with large, complex, and business-critical systems in industries such as telecom, media, TV, and the public sector. His main interests are service-orientation, domain-driven design, event-driven architectures, and open sociotechnical systems. His mantra: Great solutions emerge from collaborative sense-making and design.

Software teams often reach for Kubernetes or similar prepackaged answers as default solutions to complex problems. But Kubernetes isn’t a strategy—it’s a tool. Using it prematurely can bury your team in unnecessary complexity and unwanted consequences. These ‘default’ answers reflect a deeper issue: we don’t understand the problem we're solving.

Through real-world examples, we’ll discuss how to think critically about the way decisions are being made in your company. We’ll introduce concepts like participation theater—when people perform the rituals of decision-making without making real decisions—alongside problem restatement as a tool to uncover the real challenge at hand. We’ll also examine different types of decisions (reactive vs. proactive, reversible vs. irreversible) and why recognizing them early changes how you should approach them.

This talk is a call to slow down to speed up your decision-making. Whether you're an engineer, architect, or tech lead, this session will challenge you to pause before reaching for Kubernetes (or other technologies) and instead ask: what problem am I really trying to solve?

About Gien

Gien Verschatse is an experienced consultant and software engineer that specialises in domain modelling and software architecture. She has experience in many domains such as the biotech industry, where she

specialised in DNA building. She's fluent in both object-oriented and functional programming, mostly in .NET. As a Domain-Driven Design practitioner, she always looks to bridge the gaps between experts, users, and engineers.Gien is studying Computer Science at the OU in the Netherlands. As a side interest, she's researching the science of decision-making strategies, to help teams improve how they make technical and organisational decisions. She shares her knowledge by speaking at international conferences.And when she is not doing all that, you'll find her on the sofa, reading a book and sipping coffee.

When it comes to giving software teams the autonomy to make their own decisions, trust can be a delicate thing. This is particularly true when those decisions can have a wider impact on other teams and the overall system. If organizations are shifting towards decentralized decision-making, how do they replace the safety net of authority with trust through practices that put accountability closer to where the work happens?

In this session, we'll explore the paradox between centralized and decentralized decision-making. We'll discuss how a centralized approach aims to prevent mistakes but can also block teams from developing business-centric solutions, while a decentralized approach can lead to more sustainable decisions and empowered teams.

This will be an interactive, 1-2-all session. Andrea and Kenny will each present for ten minutes on their practices and experiences, followed by a ten-minute dialogue. The session will then open up to everyone for a broader conversation. We'll use a Miro board for sense-making exercises to help us model and explore these ideas together.

In this talk, we’ll explore quality as an emergent property of our teams, tools, and processes—not just something we test at the end. We’ll look at challenges like speed to market and enshittification(1), and how they impact our approach to quality.

We’ll introduce practical ways to think about quality through attributes like testability, observability, and recoverability. Most importantly, we’ll explore why a quality strategy—not just a testing strategy—is key to building better products.

(1) “Enshittification is a pattern in which two-sided online products and services decline in quality over time” by Cory Doctorow source

I’m an electronic engineer by trade, but software testing found me while I was working on Layer 4 protocols—and I’ve been hooked ever since. In the past, I taught software testing as an adjunct professor at UTS. These days, I work in engineering leadership, consult with teams on quality I bring a systems thinking lens to building quality in products, shaped by years working across startups, enterprises, and tech companies. I also wrote The Quality Coach’s Handbook, which you can find on Amazon or Leanpub.

"I would have killed that if it was just me, 100%,” said Spotify founder and CEO Daniel Ek about Discover Weekly, a feature that would become one of Spotify’s most loved product features, almost a brand in itself.

Designers and senior engineers were equally skeptical, but the team was still able to ship the feature.

In this talk, you’ll learn how Spotify’s organisational culture of Agile management and autonomous teams enables innovation, using the Discover Weekly feature as an example.

Joakim Sundén is a founding partner of Better Product Work,

where he helps visionary leaders challenge the conventional way of

building products. From 2011 to 2017, he worked as a Senior Agile Coach

at Spotify, where he was part of a team collaborating with the CTO to

develop the company’s approach to customer-focused product development

at scale. This model would later become world-famous as ‘the Spotify

Model’ of Tribes, Squads, Chapters, and Guilds. He now assists leaders

in transforming and improving their organizations into models where

employees are empowered to create innovative solutions that not only

customers love but also drive business success.

Did you know that crows are better than toddlers at generating novel solutions? It's true! In the earliest days of childhood, around the globe scientists have documented that human cognition struggles to generate novel solutions. But we are adept at imitation, transmitting and teaching the solutions that we see others put into practice. What does this have to do with software, and innovation, and the cultures we want to create for the communities we love? I'm a psychologist fascinated by cycles of innovation in developer communities, and I think a simple reframe lights the way forward for our industry: in this talk, rather than focusing on what drives individual developer productivity, together we’re going to focus on the science of what drives developers’ collaborative problem-solving. We'll dive into the cognitive architecture of problem-solving, as well as what I've learned from leading empirical research with thousands of developers.

Cat Hicks is a psychologist for software teams and defender of the mismeasured. She is the author of the Developer Thriving framework, the AI Skill Threat framework, and the VP of Research at Pluralsight. Cat is the founder of the Developer Success Lab, an open science research lab that creates empirical evidence about how organisations and individuals can achieve sustainable, resilient innovation in technology and create more well-being for technologists. Cat is also the founder of Catharsis Consulting, a scientific consultancy that connects organisations to human-centred evidence strategies. Cat holds a Ph.D. in Quantitative Experimental Psychology from UC San Diego, serves on the Advisory Council of the University of San Diego Center for Digital Civil Society, and is the author of a forthcoming book on the psychology of software teams.

Have you ever wondered about what makes a good abstraction vs a bad one? Do you want to examine potential reasons why efforts to develop abstractions at a company or in a project take hold, and some don't? Or what it takes to develop an abstraction that reaches beyond the technical corner of your company or project and becomes something that helps actually shape how you think about the entire problem? Understanding the process of developing abstractions, especially as a leader, is really about understanding the process of grief. Even if you get to build the abstraction, it won't be the one you pictured, or envisioned. You're going to need to take the seeds you've born, carefully curated, and lovingly built up over time... And watch them die. To build an abstraction is to hold the heart of your humanity in your hands. Plant your soul into the ground, and be reborn. In this session, I'm going to introduce my thoughts on abstraction, how it works, why it sometimes works and why it sometimes doesn't, and how one can actually take an abstraction and flesh it out to the point where it takes on a life of its own. With that, you should be able to have a better grasp on how ideas can take root in a way that bridges people and domains together.

Hazel Weakly

Hazel spends her days working on building out teams of humans as well as the infrastructure, systems, automation, and tooling to make life better for others. She’s worked at a variety of companies, across a wide range of tech, and knows that the hardest problems to solve are the social ones. Hazel currently serves as a Director on the board of the Haskell Foundation, as a Fellow of the Nivenly Foundation, and is fondly known as the Infrastructure Witch of Hachyderm (a popular Mastodon instance). She also created the first official Haskell “setup” Github Action and helped turn it into an active community-maintained project. She enjoys traveling to speak at conferences, appearing on podcasts, mentoring others, and sharing what she’s learned with the world. One of her favorite things is watching someone light up when they understand something for the first time, and a life goal of hers is to help as many people as possible experience that joy. She also loves shooting pool and going swing dancing, both as a leader and a follower.